\(\text{Yield\ }\left(\%\right)=58.95-1.19*Po-0.04*Po^{2}+16.12*\frac{B}{O}-6.05*\left(\frac{B}{O}\right)^{2}+20.70*\frac{C}{S}-5.93*\left(\frac{C}{S}\right)^{2}+0.58*Po*\frac{B}{O}+1.56*Po*C/S+2.30*B/O*C/S\) (4)