An advertising agency conducted a survey and found that the number of units sold, N, is related to the amount a spent on advertising (in dollars) by the following formula:

Question

N = 1,600 + 300 ln a (a ≥ 1).
How much needs to be spent (to the nearest hundred dollars) to sell 4,000 units?

Answer 1

4000 = 1600 + 300 ln a

ln a = 8

a = e^8 = 2980 or 3000