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

### Instruction:
Frank wants to buy a new lamp for his bedroom. The cost of the cheapest lamp is $20, and the most expensive in the store is 3 times more expensive. How much money would Frank have remaining, if he currently has $90, and he buys the most expensive lamp available?

### Response:
 โคมไฟที่แพงที่สุดมีราคา 3 * 20 = $<<3*20=60>>60
ดังนั้นถ้าแฟรงค์จ่ายเงินสำหรับโคมไฟนั้น เขาจะเหลือเงิน 90 - 60 = $<<90-60=30>>30