IRP = 34 same as IRP = 32, except that
krg=1−[Sn+Sl−Slr1−Slr]n{k_{rg}} = 1 - {\left[ {\frac{{{S_n} + {S_l} - {S_{lr}}}}{{1 - {S_{lr}}}}} \right]^n}krg=1−[1−SlrSn+Sl−Slr]n