15. which of the following is accurate when discussing specific heat?

a. specific heat values for solids will never vary for different ranges of temperature.
b. the specific heat of a gas can be measured at constant volume only.
c. specific heat values for liquids will never vary for different ranges of temperature.
d. the specific heat of a gas may be measured at constant pressure

On a mild saturday morning while people are working inside, the furnace keeps the temperature inside the building at 23degreesc. at noon the furnace is turned off, and the people go home. the temperature outside is a constant 16degreesc for the rest of the afternoon. if the time constant for the building is 3 hr, when will the temperature inside the building reach 18degreesc? if some windows are left open and the time constant drops to 2 hr, when will the temperature inside reach 18degreesc?