It is a long, downhill walk (12.6 km) from the youngest rocks (270 Ma) at the rim of the canyon to the oldest rocks (2,000 Ma) at the river. Using this information, estimate how far back in time you would go with each meter along the trail.

a. 158,730 yr/m
b. 1,373 yr/m
c. 1,587 yr/m
d. 137,302 yr/m