A 3-lb roast, initially at the 50 F, was placed in 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 a refrigerator whose temperature is set at 40 F. After 10 minutes, the temperature of roast decreased by 20 degrees. When will the temperature of roast teach 80 F?