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

### Instruction:
Which prime mover had a Model of rs-18?

### Inputs:
table_name: table, columns: ['Model', 'Specification', 'Build date', 'Total produced', 'Wheel arrangement', 'Prime mover', 'Power output']

### Response:
SELECT Prime mover FROM table WHERE Model = rs-18