please answer with a full solution

Ques a) Calculate the monthly growth rate of sales that can be sustained by a firm without access to external capital, a 20% gross margin (Cost of Goods Sold = 80% of revenue) and the following working capital policies: all expenses paid upfront, 60% of revenues collected this month, the halance in 1 month 3 months of inventory is kept on hand. Linteract nf n 45%