Calculus...?

Question

The probability density function of X, the lifetime of a certain type of device (measured in months), is given by

f(x) = 0 if x < 22
f(x) = 22/ x^2 if x > 22

P(X > 45) = 22/45

The cumulative distribution function of X:
F(x) = 0 if x < 22
F(x) = ? if x > 22

(1 is not the correct answer).

Answer 1

The CDF looks like it is linear from x=22 to x=45, at which point it is 23/45