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

### Instruction:
John buys 30 ducks for $10 each.  They weigh 4 pounds and he sells them for $5 per pound.  How much profit did he make?

### Response:
The ducks weigh 30*4=<<30*4=120>>120 pounds
So he sells them for 120*5=$<<120*5=600>>600
He bought them for 30*10=$<<30*10=300>>300
So he has a profit of 600-300=$<<600-300=300>>300
#### 300