9. Oil is leaking out of a tank at a rate of R(t) gallons/hour, where t is measured in hours. Initially there are 10 gallons of oil in the tank. (a) (2 points) Write a definite integral that represents the total amount of oil that leaks out in the first two hours. (b) (4 points) Use the graph of R(t) shown below to estimate how much oil has leaked out of the tank over the first two hours. Note that this is the graph of the rate of change of water in the tank at time ._. not how much water is in the tank at time f. R(t ) 2