The temperature of water in a certain lake on a day in October can be determined by using the model y = 15.2 minus 0.537 x where x is the number of feet down from the surface of the lake and y is the Celsius temperature of the water at that depth. Based on this model, how deep in the lake is the water 9 degrees? (Round to the nearest foot.) a. 12 c. 67 b. 45 d. 30