If a gas can affect the pressure of a gas

a. volume
b. composition
c. type
d. none of the above

Can anybody me with this? ? (picture included.)

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.

Which system of units is used by only a small number of countries in the world, including the u.s.