A 3-lb roast, initially at 50 F, was placed in the 375 F oven at 4 pm. After 75 minutes, its temperature reached 125 F. After another 25 minutes, it was taken out and put in the refrigerator whose temperature is set at 40 F. After 10 minutes, the temperature of roast decreased by 20 degrees. When will the temperature of the roast teach 80 F?