Gross Margins Calculation

HI All

I was just practising and couldn’t quite remember how to do Gross Margins

I have the below query, if I remember correctly the equation is Total Sales Revenue minus COS / total Sales Revenue * 100 = %. can some one confirm

the question is as below

Based on the facts below;
1. What is the Gross Margin value?
2. What is the Gross Margin %?
3. Explain the Gross Margin %

Quantity Unit cost Unit Price
Buy Product A 60 11.00 18.00
Sell Product A 45 11.00 18.00
Buy Product B 950 14.50 29.00
Sell Product B 80 14.50 29.00
Stock at Yr End A 18 11.00 18.00
Stock at Yr End B 870 14.80 29.00

any help would be appreciated

thank you