Sales volume and sales amount under profit and loss balance of single product The unit price $100 Unit variable cost 40 fixed costs 1,000 Depreciation amount $2,000 

2. Under the two product combinations: 

a. Under the fixed cost of 20000 yuan, the sales volume and sales amount under the balance of individual profits and losses of two products a and B? 

b. The fixed cost is RMB 20000, the target profit before tax is RMB 100000, and the sales volume and sales amount under the balance of individual profits and losses of two products a and B?