With reference to main refrigeration plant give reason for each of the following operational irregularities and state how these are dealt with:

(a) Rapid loss of lubricating oil from the crankcase of a "vee" block compressor. (4)

(b) Steady "fall off" in refrigeration effect over a comparatively short period of time. (4)

(c) Excessive "icing up" at compressor suction. (4)

(d) Short cycling. (4)