In calm waters, the oil spilling from the ruptured hull of a grounded tanker forms an oil slick that is circular in shape. If the radius r of the circle is increasing at the rate of r' (t): 30 2t+4 10. Let f (x) = x, and compute the Riemann sum of over the interval [0, 1], choosing the representative points to be the midpoints of the subintervals and using a. Two subintervals of equal length (n = 2). b. Five subintervals of equal length (n = 5). c. Ten subintervals of equal length (n = 10). d. Can you guess at the area of the region under the graph of on the interval [0, 1]? 54. Credit Card Delinquency Rate The credit card delinquency rate stood at 5.7% at the beginning of 2010. It was declining at the rate of R(t) = 0.150975e -0.0275t (0 t24) percent t months later. What was the credit card delinquency rate at the beginning of 2012? Source: Federal Reserve.