im not fully understanding this questions number 15.

er account on December 1, 2027, if interest is 7.5% compounded quarterly? 15. Gerry the Gardener owed $4000 on his purchase of a new heavy-use lawn mower for his business. He repaid $1500 in 9 months, another $2000 in 18 months, and the remaining amount owed in 27 months. If interest is 10% compounded quarterly, what is the amount of the final payment