We have that the initial value of the function is the value at x=0; this is equal to 9. It shows the initial distance from the hole, when no time has passed (x=0). This is so because y has the units of distance. THe slope of the line is the quantity that shows the rate of change, namely how much a change in x is converted to a change in y. This is so because the slope has the units of y/x, namely distance over time (so it shows speed). Correct is b.