For a two stage reciprocating compressor, compression from p₁ to p₃ is with perfect intercooling and no pressure losses. If compression in both the cylinders follows the same polytropic process and the atmospheric pressure is pa, then the intermediate pressure p₂ is given by

• A. ₂ = (p₁ + p₃)/2
• B. ₂ = p₁. p₃
• C. ₂ = Pa × p₃/p₁
• D. ₂ = Pa p₃/p₁