Yes he can, because when the area of the top of the box is divided by 3/4, you get a whole number, meaning there would be no tile pieces left over, which means that he could cover the top. SEE PICTURE FOR WORK.
After an hour (4pm to 5pm) the temperature drops 18e⁻⁰˙⁶=9.9℉, so the temperature after an hour will be 68-9.9=58.1℉. (The change -18e⁻⁰˙⁶ is negative indicating a drop in temperature.)