A) Find an equation in the form y = m x + b , where x is the number of monthly minutes used and y is the total monthly of the A Fee and Fee plan.

Question

The phone company A Fee and Fee has a monthly cellular plan where a customer pays a flat monthly fee and then a certain amount of money per minute used on the phone. If a customer uses 330 minutes, the monthly cost will be $104.5. If the customer uses 690 minutes, the monthly cost will be $194.5.

A) Find an equation in the form  where  is the number of monthly minutes used and  is the total monthly of the A Fee and Fee plan.

B) Use your equation to find the total monthly cost if 765 minutes are used.

Answer 1

M is the price per minute and also the SLOPE

B is the flat monthly fee and also the intercept...

ZER0 minutes used STILL costs $B flat fee wether you

use the phone or not?

As given x is the # of minutes used and y is the cost.

(330,104.50) and (690,194.5)

the slope is m = (194.5 - 104.50)/(690-330)

= 90/360

= 1/4

= 0.25

so it is 25 cents = $0.25 per minute

The intercept B= y - mx

= 104.50 - (0.25)(330)

= 104.50 - 82.5

= $22

THe linear cost function is therefore

y = 0.25x + 22 = C(x)

C(765) = 0.25 * 765+22 = $213.25