X(y) is the total number of androids(millions) sold in year y. A(y) is the number iphones (in millions) sold in year y. the total number of phones sold in year Y is X(y) + A(y). X(15)=550, E(15)= 75, X'(15)=0.2 and E'(12)=0.7

An iphone cost $150 on average, while the price of an android is a function F(y), with F(12)=16. What does F'(12) represent? Write an expression for total amount B(y) (in millions of dollars) spent on phones in year y. For what values of F'(12) is B'(y) positive?

Question

X(y) is the total number of androids(millions)  sold in year y. A(y) is the number iphones (in millions) sold in year y. the total number of phones sold in year Y is X(y) + A(y).  X(15)=550, E(15)= 75, X'(15)=0.2 and E'(12)=0.7

An iphone cost $150 on average, while the price of an android is a function F(y), with F(12)=16. What does F'(12) represent? Write an expression for total amount B(y) (in millions of dollars) spent on phones in year y. For what values of F'(12) is B'(y) positive?