Word problem for Rate of change formulas

[Dazed]

Here is the problem:

The marketing division of a large firm has found that it can model the effectiveness of an advertising campaign by S(u) = 0.75√u + 1.8, where S(u) represents sales in millions of dollars when the firm invests u thousand dollars in advvertising. The firm plans to invest u(x) = -2.3x^2 + 53.2x +249.8 thousand dollars each year x years from now.

1. Write the formula for predicted sales x years from now.

2. Write the formula for the rate of change of predicted sales x years from now.

3. What will be the rate of change of sales in 2000?

Can someone please help....

 

[stapel]

1) Find S(u(x)).

:shock: I just noticed what that spells...

Somebody so did not proof this question before putting it in the book. :lol:

2) Differentiate the above.

3) Um... what is the base year? The exercise says "x years from now", but this is 2005. Are we really supposed to use negative time? You might want to ask about this.

Eliz.