Explain carefully the distinction between gross and net profit. Why is the distinction considered important? Indicate whether each of the following items incurred by a manufacturing business affect the gross or the net profit, and give your reasons:

(i) Import duty paid on goods for resale.

(ii) Carriage paid to deliver goods sold.

(iii) Discount received from creditors.

(iv) Employers' National Insurance contributions paid for production workers.

(v) Holiday pay for production workers.

(vi) Advertising a product range.

(vii) Advertising for the post of works manager.