Chapter 1 - Section 1.2 - Functions and Models - Exercises - Page 77: 69

The cost of downloading a movie is 4 dollars in January, and it declines by 0.2 dollars each month past January.

The cost of downloading a movie is 4 dollars in January, and it declines by 0.2 dollars each month past January. Here, the analytical thinking and our model implies, that the function describing the values is: $C(t)=4-0.2t$