Match the following words to their definitions: 

a. Perpetual inventory system. 

b. Periodic inventory system. 

c. Gross profit. 

d. Sales revenue.

1. The primary source of revenue in a merchandising company. 

2. An inventory system under which the company keeps detailed records of the cost of each inventory purchase and sale, and the records continuously show the inventory that should be on hand. 

3. An inventory system under which the company does not keep detailed inventory records throughout the accounting period but determines the cost of goods sold only at the end of an accounting period. 

4. The excess of net sales over the cost of goods sold.