The efficiency of the vane blower is (where W₁ = Workdone due to compression, and W₂ = Workdone due to back flow)

• A. W₁/(W₁ + W₂)
• B. W₂/(W₁ + W₂)
• C. (W₁ + W₂)/W₁
• D. (W₁ + W₂)/W₂