Pharma Plus Inc. provides the following comparative financial data for the past three years.

Description	2021	2020	2019
Sales	$12,000,000	$11,500,000	$11,000,000
Cost of Sales	$7,200,000	$6,900,000	$6,600,000
Gross Profit	$4,800,000	$4,600,000	$4,400,000
Research and Development	$1,200,000	$1,150,000	$1,100,000
Selling and Administrative	$2,400,000	$2,300,000	$2,200,000
Total Operating Expenses	$3,600,000	$3,450,000	$3,300,000
Operating Income	$1,200,000	$1,150,000	$1,100,000
Other Income	$240,000	$230,000	$220,000
Earnings Before Tax	$1,440,000	$1,380,000	$1,320,000
Tax Expense	$288,000	$276,000	$264,000
Net Income	$1,152,000	$1,104,000	$1,056,000

Requirements:

1. Calculate the Gross Profit Ratio for each year.
2. Determine the R&D Expense Ratio for each year.
3. Compute the Operating Margin for each year.
4. Evaluate the trend in profitability over the three years.