
a) Here, we want to write an equation representing the total cost in relation to the number of hours
The total cost is to be represented by C while the number of hours is to be represented by t
The total cost is the dependent variable (y-value) while the number of hours t is the independent variable (x-value)
So, the linear model with respect to the above will be;

b) Here, we want to compare costs
To do this, we need to get the cost of 12 hours of recording
What we simply need to do here is to substitute the value of 12 for t in our linear model
Mathematically, that would be;

Looking at the costs, we can see that purchasing the software is a better option since it costs less