Given:
The demand function is

The cost function is

a)
Required:
We need to find the revenue function.
Step-by-step explanation:
Multiply the demand function by x to find the revenue function.




Answer:

b)
Required:
We need to find the profit.
Step-by-step explanation:
Recall that Profit=Revenue -Cost.




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Answer:

c)
Required:
We need to find the maximum profit.
Step-by-step explanation:
Consider the profit function.

Differentiate this function with respect to x.


Set P'(x) =0 to find the value of x that maximizes profit.

Subtract 840 from both sides.


Multiply both sides by (-10).


Substitute x =8400 in the profit function to find the maximum profit.


Answer:
The value of x that maximizes profit is 8400.
The maximum profit is $3,522,000.
d)
Required:
We need to find the price charged to maximize the profit.
Step-by-step explanation:
Substitute x =8400 in the demand function.


Answer:
The price charged to maximize the profit is $500.