Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
When did the tom smith built train enter service with a number under 7007?

### Inputs:
table_name: table, columns: ['Number', 'Locomotive type', 'Wheel arrangement', 'Builder', 'Entered Service', 'Withdrawn']

### Response:
SELECT AVG Entered Service FROM table WHERE Builder = tom smith AND Number < 7007