Demand: Smart Phones (See Exercise 35.) Here is another model for worldwid...

Demand: Smart Phones (See Exercise 35.) Here is another model for worldwide demand for smart phones:

million units sold annually (50 ≤ p ≤ 150),

where p is the unit price in dollars.26

a. Graph the demand function.

b. Use the demand function to estimate, to the nearest million units, worldwide sales of smart phones if the price is $70.

c. Extrapolate the demand function to estimate, to the nearest million units, worldwide sales of smart phones if the price is $180.

d. Model the worldwide annual revenue from the sale of smart phones as a function of unit price, and use your model to estimate, to the nearest billion dollars, worldwide annual revenue when the price is set at $70. HINT [Revenue = Price × Quantity = p ? q(p)]