What can a firm do to increase productivity in the short run once its marginal product is zero? Increase the quantity of the input.
Decrease the quantity of the input.
Lower the price of its product.
Raise the price of its product.
Nothing, as more workers decreases total product.

  Decrease the quantity of the input

Step-by-step explanation:

The general assumption is that productivity is a curve that is concave downward, Hence marginal product is decreasing until it reaches zero. The way to increase it is to reduce the input quantity to a value below the point where the curve reaches zero marginal product.