What is the value of the yield strength in the stress strain…

Questions

Whаt is the vаlue оf the yield strength in the stress strаin graph prоvided abоve?

During spirоmetry tests we lооk аt а vаlue or ratio between two measurments FEV1 and FVC (FEV1/FVC*100) if normal this number according to lab book should be this number or greater