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

### Instruction:
What number has the builder ruston hornsby, the date 1961, and the name Topsy?

### Inputs:
table_name: table, columns: ['Number', 'Name', 'Builder', 'Type', 'Works number', 'Date']

### Response:
SELECT COUNT Number FROM table WHERE Builder = ruston hornsby AND Date = 1961 AND Name = topsy