I need to isolate contribution of a single entity in a Division of Sums as shown below. For example, find the contribution of variable a in the following:
(a 1 + b 1 + c 1) / (a 2 + b 2 + c 2)
Example with numbers:
| Stock | $ Earnings | $$ Sales |
|---|---|---|
| AAPL | 10 | 100 |
| MSFT | 25 | 50 |
| AMZN | 5 | 50 |
Profit Margin = (10+25+5)/(100+50+50) = 20%
I need to break down this 20% into contribution by only AAPL for example.