On January 1, 2009, David owed $9,452 to his friend Mackenzie, who was kind enough not to charge David any interest. Each month during 2009, David paid Mackenzie some of the money he owed. If David still owed Mackenzie $5,876 on January 1, 2010, what was the average amount of David's monthly payments?

$68.44 for each additional belt

Step-by-step explanation:

The cost and revenue functions are:

The profit function, P(x), is given by subtracting the cost function from the revenue function.

The derivate of the profit function gives us the rate at which profit changes:

For x = 484, the rate of change is:

Profit is increasing by $68.44 for each additional belt