A firms production function is given by (a) Write down expressions for the marginal product of labour

Question:

A firm’s production function is given by (a) Write down expressions for the marginal product of labour and marginal product of capital.
(b) The firm currently uses 18 units of capital and 50 units of labour, and decides to reduce the level of labour to 49 units. Estimate the corresponding increase in capital if output is to remain unchanged.