Answer:
a. x represents income earned
Explanation:
Using the model, which is the equation of a line or regression model.
y = mx + c
The base amount of $1000 which is always included is constant, this represents c, the intercept.
x in the equation is the independent variable, which is the income earned, and dictates the change in the amount spent y
m = 1/2 which dictates the proportion of the income earned that is spent.
y = the amount which is spend