A company manufactures circuits wired in series that use 2 LEDs and a resistor to light up a display screen. Each LED has a known internal resistance of 127.5Ω, optimally operates at .015 Amps, and will be damaged at any current above .020 Amps. Analyze the circuit and determine the proper size resistor needed if they use a 15v power supply.

An air-conditioning system consists of a heating section and an evaporative cooler. air enters the heating section at 10°c and 70 percent relative humidity at a rate of 30m^3/min, and it leaves the evaporative cooler at 20°c and 60 percent relatively humidity. if the air conditioning system operates at a total pressure of 98 kpa, determine (a) the temperature and relative humidity of the air when it leaves the heating section, (b) the rate of heat transfer in the heating section, and (c) the rate of water added to air in the evaporative cooler