A cake recipe says to bake a cake until the center is 180 degrees then let it cool to 110 degrees. If I have a table that says at 5 minutes the cake is 124 degrees, at 10 minutes the cake is 92 degrees, at 15 minutes the cake is 78 degrees and at 20 minutes the cake is 70 degrees. What is an exponential model for this data if the room temperature is 68 degrees