(a) Quantity demanded = 160 - 2p

Quantity supplied = -40 + 2p

Equlibrium is attained at a point where market demand is equal to market supply, i.e.

Quantity demanded = Quantity supplied

Hence, \(160-2p=-4p+2p\\ 160+40=2p+2p\\ 200=4p,\quad p=\frac { 200 }{ 4 } =50\)

Hence, equilibrium price = Rs.50

Equilibrium quantity will be,

Quantity demanded = Quantity supplied

\(=160-20=160-2\times 50\\ =160-100=Rs.60\)

(b) At any price below the equilibrium price, there will be excess demand.

Let us take at price Rs.20

At p = Rs.20

\(Quantity\quad demanded\quad =160=-2p\\ \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad =160-2\times 20=160-40\\ \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad =Rs.120\\ Quantity\quad supplied\quad =\quad -40\quad +\quad 2p\\ \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad =\quad -40\quad +\quad 2\times 20\quad =\quad -40\quad +40\\ \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad =0\)

Quantity demanded

> Quantity supplied [ excess demand]

Also, it can be concluded that at Rs.20 there will be no supply of the commodity, hence between 20 < p < 50, there will be excess demand.

(c) At any price above equilibrium, there will be excess supply.

Let us take at price Rs.80

\(Quantity\quad demanded\quad =160-2p\\ \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad =160-2\times 80=160-60\\ \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad =0\\ Quantity\quad supplied\quad =-40+2p\\ \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad =-40+2\times 80=-40+160\\ \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad =120\)

Quantity demanded

<Quantity supplied [excess supply]

Also, it can be concluded that at p=Rs.80 demand will be zero, hence there will be excess supply between 50 < p < 80.