How can producers maximize their profit? Check all that apply

How can producers maximize their profit? Check all that apply.

a. They can work to increase their marginal cost.
b. They can work to decrease their marginal cost.
c. They can raise prices to increase marginal revenue.
d. The can lower prices to decrease marginal revenue.
e. They can keep marginal costs below marginal revenues.
f. They can keep marginal revenues below marginal costs.