Marcos purchases a top-up card for his pre-paid cell phone. his remaining balance, b, can be modeled by the equation b=40−0.05n, where n is the number of minutes he's talked since purchasing the card.
a) how much money was on the card when he purchased it? $. which intercept is this?
b) how many minutes will he have talked when he runs out of money? $. which intercept is this?
c) what is the slope of this equation? . what are the units on the slope?