Answer:
The correct option is 1.
Step-by-step explanation:
If a line passing through two points then the slope of the line is

Choose any two points of function 1:
Let the points are (1,80) and (2,75). The rate of change of function 1 is

It means Galvin spends $5 each month.
Henry's money deifned by the equation
.... (1)
The slope intercept form of a line is
... (2)
From (1) and (2) we get

It means Henry's spends $7 each month.
Function 2 shows a greater rate of change, because Henry spends $7 each month and Galvin spends $5 each month.
Therefore the correct option is 1.