Heating

Hello, I need help with this question:

On a hot Saturday morning while people are working inside, the air conditioner keeps the temperature inside the building at 24⁰C. At noon, the air conditioner is turned off, and the people go home. The temperature outside is a constant 35⁰C for the rest of the afternoon. If the time constant for the building is 4 hours, what will be the temperature inside the building at 2:00 PM? At 6:00 PM? When will the temperature inside the building reach 27⁰C? (Answers: 28.3⁰C, 32.5⁰C, 1:16 PM)