I can't solve this physics problems, i've been trying for 2 days straight and i still can't solve them, i had to rewrite the questions because my handwriting is horrible, this is basically a repost with another image, my teacher isn't answering questions either so i am lost with this problems

Acoal-fired plant generates 600 mw of electric power. the plant uses 4.8 x 10^6 kg of coal each day, and the heat of combustion of coal is 3.3x 10^7 j/kg. the steam that drives the turbines is at a temperature of 300° c, and the exhaust water is at 37° c. (a) what is the overall efficiency of the plant for generating electric power? (b) how much thermal energy is exhausted each day? (c) what is the change in entropy of the universe for this heat engine? (d) using the same heat reservoirs, what is the maximum possible (carnot) efficiency for a heat engine?

Alfred pushes on a heavy box, but cannot move it. the box has a lot of inertia motion friction gravity

Balloon a has charge q, and identical mass balloon b has charge 10q. you hang them from threads near each other. choose all of the statements with which you agree. check all that apply. a. a and b exert the same magnitude forces on each other. b. the force that a exerts on b is 10 times the force that b exerts on a. c. the angle between the thread supporting a and the vertical is < the angle between the thread supporting b and the vertical. d. the force that a exerts on b is 1/10 the force that b exerts on a.