In vietnam, a conventional force (the unites states) opposed a guerilla force (the vietcong). this conventional foce y(t) is out in the open to be shot at; its combat loss rate is limited only by the number of the x-force that can shoot. so the model for vietnam is dx/dt = -ady, dy/dt = -bx.

Two kilograms of air within a piston–cylinder assembly executes a carnot power cycle with maximum and minimum temperatures of 800 k and 300 k, respectively. the heat transfer to the air during the isothermal expansion is 60 kj. at the end of the isothermal expansion the volume is 0.4 m3. assume the ideal gas model for the air. determine the thermal efficiency, the volume at the beginning of the isothermal expansion, in m3, and the work during the adiabatic expansion, in kj.