Answer:
Function B has a greater rate of change since it has a greater slope
Explanation:
The slope for function A
m= (y2-y1)/(x2-x1)
 = (15-13)/(6-5)
 = 2/1
 =2
The slope for function B 
We have 2 points ( (1,1) and (2,4)
m= (y2-y1)/(x2-x1)
 = (4-1)/(2-1)
 =3/1
 =3
Function B has a greater rate of change since it has a greater slope