Question: a the total cost function is given by cx ...
a. The total cost function is given by C(x) = −2x3 +
70x2− 315x + 450,where x is the number of units produced
and sold. Show that x = 30 units of output is the only
real output level at which total cost will be zero.
b. At the end of an advertising campaign,monthly sales of cell phones declined according to the equation S(t) = 150(4−0.03t) thousand dollars, where t is the number of months
after the campaign ended.
i. What will be the level of sales at the end of the campaign?
ii. What will be the level of sales 3 years after the end of the campaign
iii. How many months will it take on average for monthly sales to reach $80,000?