***4.1.22. A manufacturer of briquettes has a contract to make briquettes for barbecuing that are guaranteed to not contain over 10% moisture or 10% ash. The basic material used has this analysis: moisture 12.4%, volatile material 16.6%, carbon 57.5%, and ash 13.5%. To meet the specifications (at their limits) the manufacturer plans to mix with the base material a certain amount of petroleum coke that has this analysis: volatile material 8.2%, carbon 88.7%, and moisture 3.1%. How much petroleum coke must be added per 100 lb of the base material