Below is an instruction that describes a task. Write a response that appropriately completes the request in English. Please answer in English.

### Instruction:
Jack and Jill are friends who borrow from each other often. Last week Jack borrowed  $1200 from Jill, which he promised to pay back with an interest of 10%. How much will Jack pay back?

### Response:
Initially, Jack owed Jill $1200, but since he will pay an interest of 10%, he will pay $1200 + ($1200 * 10%) = $1200 + $120 = $<<1200+120=1320>>1320
#### 1320