We can measure the rate of erosion in this canyon at about $0.01$ inches/year. Based on this rate, when did the canyon start to erode? (Hint: Measure the difference in elevation from the bottom of the canyon at the latitude and longitude given above and the top, measured at the road on the edge of the canyon due south of the previous point. Then divide by the rate of erosion. Make sure to use the correct units.)
a. 750,000 years
b. $1,200,000$ years
c. $2,700,000$ years
d. $3,500,000$ years