Express the following relationships as formulas:

(a) Revenue, gross profit, and net profit.

(b) Opening inventory, closing inventory, purchases, and cost of sales.

(c) The balance brought forward on an expense account, the other transactions recorded in the expense account, the balance carried forward on the account, and the amount treated as an expense in the income statement.

(d) The opening balance on a sole proprietor’s capital account, drawings, net profit, and the closing balance on the capital account.