How can i determine the ultimate and yield strengths of the material prior to forming; the yield strength of the material at the corners of the section after cold forming and the average yield strength of the section?

Most leaks in reciprocating air compressors can be detected and minimized by: (clo4) a)-detecting leakage areas using ultrasonic acoustic detector. b)-tightening joints and connections c)-replacing faulty equipment d)-all of the given options