I need help solving this problem: A savings account is opened and an initial deposit of 2000 is made at t = 0. Six months later, a withdrawal of 400 is made. One year after the account was opened, a withdrawal of 400 was made, and 1.5 years after the account was opened, a withdrawal of 300 was made. Then for the next six months, no deposits or withdrawals were made. The balance two years after the account was opened was 1100. Assuming the savings account grows according to compound interest, find the annual effective interest rate for the account.