Given two points (x₁,y₁) and (x₂,y₂) the rate of change is the slope (m) of the line
passes through these points.
m=(y₂-y₁)/(x₂-x₁)
We have two points:
(2,200)
(6,760)
Rate of change=m=(760-200)/(6-2)=560/4=140 ft/h
Answer: the rate of change would be 140 ft/h.
