All of these

Consumer preference

Freedom of enterprise

Interrelated to each other

Income from the railways (as it refers to an individual industry).

MRT is the rate at which the units of one good have to be sacrificed to produce one more unit of the other good in a two goods economy. Suppose an economy produces only two goods X and Y. Further suppose that by employing these resources fully and officiently, the economy produces 1X + 10Y. If the economy decides to produce 2X, it has to cut down production of Y by 2 units. Then 2Y is the opportunity cost of producing 1X. Then 2Y:1X is the MRT.

An economy has millions of commodities to produce.  It has to decide which goods and services to be produced and that should be in sufficient quantity, as all the goods cannot be produced due to scarcity of resources. e.g. an economy has to decide whether to produce luxury goods or inferior goods, capital goods or consumer goods.
This problem has two dimensions:
(i) Types of goods to be produced.
(ii) Quantity of goods to be produced.

The problem of 'how to produce' is a problem relating to choice of techniques.  Broadly, it is the problem of deciding the techniques of production which are to be used.
There are two type of techniques of production, which are as follow:
(i) Labour intensive technique It is that technique in which labour is used more than capital.
(ii) Capital intensive technique It is that technique in which capital is used more than labour.

This is very correct to say that only scarce goods are high in price.  This can be supported by the water, diamond paradox.  Though water is very useful for all living being, however, it is very low priced as it is available in plenty.  On the other hand, diamond which is not so useful is still very high in price due to its relative scarcity.

Economics is concerned with the study of economic problems at the level of an economy as a whole, on one side and on the other, it is concerned with the study of an individual too. The subject matter of economics is studied under two broad branches viz microeconomics and macroeconomics.
Vital theories or studies of microeconomics are:
(i) Theory of consumer behaviour.
(ii) Theory of price.
(iii) Theory of producer behaviour.
Vital theories or studies of macroeconomics are:
(i)Theory related to equilibrium level of output and employment.
(ii) Theory related to inflationary and deflationary gap in the economy.
(iii) Theory of multiplier.
(iv) Study of government budget.
(v) Study of exchange rate and Balance of Payments (BoP).

Examples of microvariables are:-
(i) Consumer's demand
(ii) Market price of a commodity
(iii) Firm's output (supply)
Examples of macrovariables are:
(i) Aggregate Demand in the economy.
(ii) General price level in the economy.
(iii) Aggregate Supply in the economy.

With the death of lot of people due to severe earthquake, working force in a country will fall. Similarly, destruction of factories will cause a reduction in the stock of capital in a country. Thus, earthquake causes decrease in labour 'and capital resources of a country. This decrease in resources causes a shift of production possibilities curve to the left showing less production of both the goods than before.

MOC or MRT is defined as the addition made to the cost in terms of number of units of a good sacrificed to produce one more unit of the other goods.
                                       Schedule

In the given schedule, there are five combinations. Combination A depicts none of X and all of Y and combination E denotes nothing of Y is produced and all resources are utilised to produce Y. In combination B, to produce 1 unit of X, one unit of Y is sacrificed. In this way we observe that to have one more unit of X, 1Y, 2Y's, 3Y's and 4Y's are sacrificed respectively. This shows the increasing rate of sacrifice or MOC.

An economic problem mainly arises on account of the scarcity of the resources available to satisfy the unlimited human wants. To a large extent, if the resources were not limited, the economic problem would not have arisen, because every want could be satisfied, i.e., everyone could have everything. But this indeed is not true as the reality is that relative scarcity will continue to prevail and the other related problem -of 'choice' would always exist. One is always confronted with the problem of what to choose and what to give up, i.e., sacrifice. Thus, scarcity, being a relative term, will always exist and so would an economic problem.