What is the y-intercept of the line connecting (1,5) and (4,14)?

a. b = 5
b. b = 14
c. b = 2
d. b = –14
e. none of these

The answer is C. b=2.
I found the answer by first finding the slope. To find the slope i found the difference of the y values and divided that by the difference of the x values. 
14-5/4-1
This simplifies down to:
9/3 which equals 3.
I then plugged this into the slope intercept form: y=mx+b to get y=3x+b
The next step would be to plug in the values of one of the points to solve for b. The point I choose was (1,5). By plugging this point into the equation i got 5=3(1)+b which simplifies to 5=3+b which means that b=2

D) the x-intercept represents adam's commission pay when he had zero total sales