12.Find the rate of change for each function.

Function A

Mandy's monthly cell

phone bill is represented

by the function

y=0.10x + 70, where x

represents the minutes

and y represents the cost.

Function B

Angel's monthly cell

phone bill is

represented by the

function y=0.25x + 30,

where x represents the

minutes and y

represents the cost.

4. How much more expensive is

Function C than Function D if they

talk for 200 minutes each?