 Solution

ID: past-exam-of-the-mathematical-methods-ii-course-of-the-university-of-oxford/2021-resit/7/a/solution

The probability density function is nonnegative and vanishes on negative lifetimes. Since

0.04 = 1/25

\int_{- \infty}^{\infty} f_{T} (t) d t = \int_{0}^{\infty} \frac{1}{25} e^{- t /25} d t = [- e^{- t /25}]_{0}^{\infty} = 1.

1/25

per month.

 New to topics? Read the docs here!