Word Problem: Differentiation (selling bottles of perfume)

sfgiants

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Oct 2, 2007
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I'm having trouble figuring out how to set up the equation in the following word problem.

Bea Johnson, the owner of the Bea Nice boutique. estimates that when a particular kind of perfume is prices at p dollars per bottle, she will sell

B(p) = 500/p+3 if p is more than or equal to 5.

bottles per month at a total cost of

C(p) = 0.2p^2 +3p +200 dollars.

a) Express Bea's profit B(p) as a function of the price p per bottle.
b) At what rate is the profit changing with respect to p when the price is $12 per bottle? Is profit increasing or decreasing at that price?


Once I get part a), I think I can get part b) by differentiating my answer to part a).

My problem is that I do not understand how to set up the equation for part a.

Any help would be greatly appreciated.

Thanks!
 
Hint: What is the definition of "profit", particularly with respect to "income" versus "cost"? What is the definition of "total income", particularly with respect to "total units sold" and "per-unit price"?

:wink:

Eliz.
 
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