PQR Ltd. is engaged in the production and sale of textiles. Given below are the financial results for the last three years.

Description	2021	2020	2019
Sales	$3,000,000	$2,400,000	$2,000,000
Cost of Goods Sold	$1,800,000	$1,440,000	$1,200,000
Gross Profit	$1,200,000	$960,000	$800,000
Operating Expenses	$300,000	$240,000	$200,000
Operating Profit	$900,000	$720,000	$600,000
Other Income	$60,000	$48,000	$40,000
Earnings Before Tax	$960,000	$768,000	$640,000
Tax	$192,000	$153,600	$128,000
Net Profit	$768,000	$614,400	$512,000

Requirements:

1. Calculate the Gross Profit Ratio for each year.
2. Determine the Operating Profit Ratio for each year.
3. Compute the Earnings Before Tax Margin for each year.
4. Analyze the change in profitability over the three years.