The temperature a of water in an ice cube tray is 75 F when it is placed in a freezer Its temperature n hours after being placed in the freezer is 20 less than 1 hour earlier a Find a formula for the nth term of the geometric sequence that gives the temperature of the water n hours after it is placed in the freezer an b Find the temperatures of the water 6 hours and 12 hours after it is placed in the freezer Round your answers to two decimal places a6 a12 F F c Use a graphing utility to graph the sequence to approximate the time required for the water to freeze Round your answer to one decimal place hr