A company charting its profits notices that the relationship between the number of units sold, x, and the profit, P, is linear. If 170 units sold results in $1340 profit and 220 units sold results in $3940 profit, write the profit function for this company and find the marginal profit in dollars. I was able to find the profit function: p=52/1x - 7500 but I cannot find the marginal profit. Please show your work, so I can understand it.