There are four primary rules of firearm safety. One of these rules is: Unload firearms when not in use.

Unload a firearm before climbing a fence or tree.

Avoid alcoholic beverages before and during shooting.

Be sure of the target, what is in front of it, and what is beyond it.

To save energy, the air supply to a 2000 ft office has been shut off overnight and the room temperature has dropped to 40°f. in the morning, the thermostat is reset to 70°f and warm air at 120 f begins to flov in at 200ft'/min. the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct. the air pressure is nearly 1 atm everywhere. ignoring heat transfer with the surroundings and kinetic and potential energy effects, estimate how long it takes for the room temperature to reach 70°f. plot the room temperature as a function of time.