A pneumatic system requires an average delivery volume of 20 m 3 min 1 free air delivery. The air compressor has a rated free air delivery of 35 m 3 min 1, a working gauge pressure of 6 bar and is controlled to switch off load when the receiver gauge pressure rises to 6 bar and back on load when the receiver gauge pressure has dropped to 5 bar. Determine a suitable receiver capacity if the maximum allowable number of starts per hour for the compressor is 20.