A cell phone provider offers a plan that costs $40 per month plus $0.20 per text message sent or received. A comparable plan costs $70 per month but offers unlimited text messaging. Complete parts a. and b. below.
a. Write an equation for the cost y (in dollars) of x text messages for the $40 per month plan.
y = 40 + 0.20x
b. Write an equation for the cost y (in dollars) of x text messages for the $70 per month plan.
y = 70