please help me with this question with explain!

lionel plans to make equal deposits at the beginning of each year for 10 years into an account that pays interest of 5% compounded annually. His goal is to accumulate $50000 after 10 years. a. What is the size of the equal deposits he wii have to make to accomplish this goal? b. suppose Lionel make equal payments at the beginning of each year for 7 years, but misses the payments for the last three years. How much would the equal size payments have to be in this case id his goal is still to accumulate $50000 after 10 years?