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

### Instruction:
When the network mask is 255.255.255.252 what is the prefix size?

### Inputs:
table_name: table, columns: ['Prefix size', 'Network mask', 'Available subnets', 'Usable hosts per subnet', 'Total usable hosts']

### Response:
SELECT Prefix size FROM table WHERE Network mask = 255.255.255.252