The correct option is (c) 77.8%

The best I can explain: Swept volume per hour = \(\frac{π}{4}\)*D^2*Number of cycles per hour*Number of cylinder

= \(\frac{π}{4}\)[11/100]^2*[12.2/100]*2800/2*60*6

= 584.33 m^2

Volumetric efficiency = \(\frac{Actual \,volume \,of \,air \,taken}{Swept \,Volume}\)*100

= \(\frac{455}{584.33}\)*100

= 77.8%.