A person borrows $3,000 at 6% per annum simple interest. She is to repay the debt with 4 equal payments, the 1st at the end of 3 months, the 2nd at the end of 6 months, the 3rd is due at the end of 9 months, and the final payment is due at the end of 12 months. Determine the size of the payments using the focal date of 6 months.