Due to a decrease in radiation, the mutation rate decreases linearly from 4.0 10-6/yr at t = 0 to 1.0 10-6/yr at t

Due to a decrease in radiation, the mutation rate decreases linearly from 4.0 × 10-6/yr at t = 0 to 1.0 × 10-6/yr at t = 2 × 106. Find the expected number of mutations over the course of 2 million years. What is the average mutation rate over this time?
The previous problem shows that the number of mutations follows a Poisson distribution even when the mutation rate changes. In fact, if the rate changes continuously, following some function λ(t), the number of mutations between time 0 and time t follows a Poisson distribution with mean

Use this formula to analyze the following circumstances.

1(s)ds.