need help with question in pic plz

During the design stage, we expect 150 patients per year will enter into a study to compare two treatments. Assume exponential distributions for the survival times of both treatments and assume the mean survival time for treatment 2 is 3 years. We wish to detect with 90% power that treatment 1 has mean survival time of 4 years using a twosided log-rank test at 0.05 significance level. Suppose we will enroll patients for 5 years. How long should the study last? Please include any code you used to solve this