In 'Percentage of Sales' method of preparation of Projected Financial Statements, the Operating Expenses should be projected on the basis of:

<p><strong>(a) % of Profit before tax, </strong></p> <p><strong>(b) % of Cost of goods Sold,</strong></p> <p><strong> (c) % of Gross Profit,</strong></p> <p><strong> (d) % of Sales.</strong></p> <p> </p>