Chapter 3.3, Problem 10E

Early Monday morning, the temperature in the lecture hall has fallen to $40°\text{F}$, the same as the temperature outside. At 7:00 A.M., the janitor turns on the furnace with the thermostat set at $70°\text{F}$. The time constant for the building is $1/K=2\text{hr}$ and that for the building along with its heating system is $1/K_1=1/2\text{hr}$. Assuming that the outside temperature remains constant, what will be the temperature inside the lecture hall at 8:00 A.M.? When will the temperature inside the hall reach $65°\text{F}$?