Answer:
31. c(x) = 3.00 -0.01x
32. C(x) = 3800 +3.00x -0.01x²
Step-by-step explanation:
You want an expression for cost per item and one for the manufacturing cost of x items, given the per-item cost is $3.00, minus $0.01 for every item, and the fixed manufacturing costs are $3800.
We can express the description "$3.00, minus $0.01 for every item" as the expression ...
3.00 -0.01x
The cost function will be the total of initial costs and the product of the number of items and the cost per item:
C(x) = 3800 +x(3.00 -0.01x)
C(x) = 3800 +3.00x -0.01x² . . . . . . . simplified
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Additional comment
The number sold at price p is q(p) = 100 +10(5 -p). This is maximized at 75 when the price is 7.50. However, maximum profit is had when 67 are sold at a price of $8.30. This results in weekly profit of $399.99, not enough to cover the initial cost.
Hence the cost function isn't quite right, as it mixes a one-time cost with the per-week cost. It would seem to take just over 9.5 weeks to make enough profit to cover the initial costs.