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

### Instruction:
what is the highest platform number when the frequency (per hour) is 4, the operator is london overground and the destination is west croydon?

### Inputs:
table_name: table, columns: ['Platform', 'Frequency (per hour)', 'Destination', 'Operator', 'Line']

### Response:
SELECT MAX Platform FROM table WHERE Frequency (per hour) = 4 AND Operator = london overground AND Destination = west croydon