What is the proper set-up for the equation to determine the rate at which the islands are sinking, as asked in question 12 of the lab manual on page 71? Choose the correct option:

a) rate = difference in elevation of Maui and Nihoa
b) rate = elevation of Maui divided by elevation of Nihoa
c) rate = elevation of Nihoa divided by elevation of Maui
d) rate = sum of elevations of Maui and Nihoa