X is normally distributed with mean 12 and sd 4. Find P(X ≤ 20) and P(0 ≤ X ≤ 12)

In a photographic process, the developing time of prints may be looked upon as a random variable having the normal distribution with a mean of 16.28 seconds and a standard deviation of 0.12 second. Find the probability that it will take less than 16.35 seconds to develop prints.

A manufacturer of metal pistons finds that on the average, 12% of his pistons are rejected because they are either oversize or undersize. What is the probability that a batch of 10 pistons will contain
(a) no more than 2 rejects?
(b) at least 2 rejects?

The time taken to assemble a car in a certain plant is a random variable having a normal distribution of 20 hours and a standard deviation of 2 hours. What is the probability that a car can be assembled at this plant in a period of time .
a) less than 19.5 hours?
b) between 20 and 22 hours?

X is a normally normally distributed variable with mean μ = 30 and standard deviation σ = 4. Find
(a) P(x < 40)
(b) P(x > 21)
(c) P(30 < x < 35)