For each problem, use meaningful variables to write a linear function to model the situation. Then interpret the slope and y-intercept in words. Identify which variable would be on the horizontal axis and which one would be on the vertical axis. a) Model the cost if you buy an iPod for $200 and download songs for $1.29 each.

b) Model the weekly salary a salesman earns if his salary is a combination of his base salary and commissions on his sales. His base weekly salary is $500 and he makes $50 for each sale.