1000 kg/h of a mixture of benzene (b) and toluene (t) that contains 50% w/w benzene by mass are separated by distillation into two fractions. the mass flow rate of benzene in the product top stream is 450 kg b/h and that of toluene in the bottom stream is 475 kg t/h. the operation is at steady state. write balances on benzene and toluene to calculate unknown component flow rate in the output streams