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

### Instruction:
 约翰以4美元购买爆米花袋，以8美元出售。他卖出30袋爆米花能获得多少利润？


### Response:
 每袋爆米花的利润是$8-$4=$<<8-4=4>>4
所以他总共获得的利润是$4*30=$<<4*30=120>>120