Anyone can help me to fininsh this problem and I'll appreciate that!

Peter starts a saving account and deposits $2000 into the account. The saving account earns compounded interest at an annual nominal interest rate 4.6% convertible quarterly. In addition, he has deposited $X and $2X after 6 months and 1 year respectively (a) Find the minimum value of X such that the saving account can accumulate at least $5000 by the end of 2nd year. (b) Suppose that the annual nominal interest rate of the saving account drops to 4% during 2nd year (The interest rate in the first year remains to be 4.6%). Find the minimum value of X such that the saving account can accumulate at least $5000 by the end of 2nd year