K A marine manufacturer will sell N(x) power boats after spending $x thousand on advertising, as given by N(x) = 1,040 - - 3,900 x -, 5SXS 30. 1000- AN(x) (A) Find N'(x). 900- (B) Find N'(10) and N'(20). Write a brief verbal interpretation of these results. BOO- 700- 600 Boats sold 500 400- 300 200 100 O- 0 5 10 15 20 25 30 35 Thousands of advertising dollars