Technician a states that if a vacuum gauge is hooked up to an intake manifold while the engine is idling the needle should bounce for each intake stroke of the pistons. technician b states that if the needle on the vacuum gauge is bouncing it indicates a mechanical problem with the valve train. who is correct?
a. tech a only
b. tech b only
c. both tech a and b
d. either tech a and b

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?