How to solve the 2 questions in that box

Trish receives $450 on the first of each month. josh receives $450 on the last day of each month. both trish and josh will receive payments for next four years. at a discount rate of 9.5 percent, what is the difference in the present value of these two sets of payments?

Any is very appreciated! (picture is provided below)not sure how to do this at all won't lie

Iwill give ! if m∠a=59 and m∠3=81°, what is m∠b? m∠b= _[blank]_°