For the truss under the following 3 loading conditions, determine the minimum cost of each truss based on the following:

* wood (popsicle sticks) - $100/stick

* cable (thread) - $10/section

note that all members of the truss are the same length. given this information, it doesn’t matter what length you use, or what "x" is, but if it , just make up numbers, i. e. length of 5" and x of 10lbs. in class we will be using members that are approximately 6" long and weights that are approximately ½ lb, although on the weights we can just add more to get the desired effect.

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 the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct.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.