To undo a marginal function, we need to find the antiderivative of the marginal function. In other words, the antiderivative of marginal cost is cost.

**Problem 1** Find the cost function for the marginal cost function

where 16 units cost $45.

**Problem 2** Find the cost function for the marginal cost function

where 8 units cost $58.

Similarly, the antiderivative of the marginal revenue is revenue. To find the corresponding demand function, we need to divide by x,

**Problem 3** Find the demand function for the marginal revenue function

**Problem 4** Find the demand function for the marginal revenue function