The elevation of a cyclist over time can
be modeled by a linear equation
relating the number of minutes since
the ascent started and the elevation of
the cyclist in feet. After 4 minutes, the
elevation is 940 feet. After 9 minutes,
the elevation is 1140 feet. What is the
rate of change of the elevation?

A 40 feet per minute
B 50 feet per minute
C 160 feet per minute
D 200 feet per minute