19. From the following information, calculate the cost of sales: (2 Sales $300,000 Electricity expense $5,500 Sales returns $5,000 Opening inventory $21,000 Purchases $100,000 Delivery inwards $3,000 Advertising expense $5,000 Closing inventory $10,000 Purchases returns $1,500 Delivery outwards $4,500 Customs duty $1,800 Rent expense $11,500