In London, sulfur-rich brown coal was used for a long time, and it was well-known for its thick fog due to poor combustion. The exhaust gases from the combustion of brown coal have the following molar composition on a dry basis: CO2 = 72.0% CO = 2.57% SO2 = 0.0592% O2 = 25.4% Brown coal is burned with a 20% excess of pure oxygen. There is no oxygen in the brown coal. Calculate the original composition of the brown coal in mol%. Make relevant assumptions to solve the problem.