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

### Instruction:
How many different PPI does the model with ppcm of 87 have?

### Inputs:
table_name: table, columns: ['Model', 'PPI (pixels per inch )', 'ppcm (pixels per cm )', 'Resolution', 'Typical viewing distance (in/cm)', 'Pixels per degree (PPD)']

### Response:
SELECT COUNT PPI (pixels per inch ) FROM table WHERE ppcm (pixels per cm ) = 87