Writing a function and giving a domain

Question

A local bank has a debit card that gives a $3 reward each month you use your card for $50 or more in purchases. Write an equation relating rewards earned, y, to total monthly purchases, x. give the domain of this function.

Question 2: a local credit union has a debit card that rewards 3% of your monthly purchases. Write an equation relating rewards earned,y, to total monthly purchases, x. give the domain of this function

Answer 1

Y = {$3 | x>= $50

Y = {$0 | x< $50

Domain is [0, ∞)