The waiting time between eruptions of the Old Faithful geyser in Yellowstone National Park depends upon the length in time of the last eruption. A representative sample of 10 data pairs for the eruption duration in minutes (x) and the waiting time in minutes till the next eruption (y) appears below. x 4.327 3.977 4.71 4.293 2.277 4.726 2.007 4.127 4.743 1.81
y 81 89 83 79 55 90 49 79 75 53

Required:
a. Find the least-squares line to describe the waiting time as a function of the eruption time.
b. Draw a scatterplot of the data along with the least- squares line. What unusual feature do you see? Can you think of any way to explain this feature?