A painter and his helper are standing on a scaffold. The painter weighs 400 newtons. The helper weighs 300 newtons. The tension in a rope A is 925 newtons. The tension in rope B is 825 newtons. What Is the weight of the board?

Air is to be preheated by hot exhaust gases in a cross-flow heat exchanger before it enters the furnace. air enters the heat exchanger at 95 kpa and 20°c at a rate of 0.6 m^3/s. the combustion gases (cp = 1.10 kj/kg°c) enter at 160°c at a rate of 0.95 kg/s and leave at 95°c. determine the rate of heat transfer to the air and its outlet temperature.