A car laps a race track in 84 seconds. The speed of the car at each 6-second interval is determined by using a radar gun and is given from the beginning of the lap, in feet/second, by the entries in the following table. Time 0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 Speed 124 134 148 156 147 133 121 109 99 85 78 89 104 116 123 How long is the track? I