Cumulative yield calculation

I am trying to create a report which shows the calculation of the cumulative product yield.  Yield from initial raw material to the final finished good product.  Example:

Item ABC yields 20,000 lbs.  Initial raw material input of item RM123 was 20,559.  This is a yield of 97.3%  (20,000 lbs / 20,559 lbs).

A portion of the item ABC (8,000 lbs) is used as ingredient for the Item DEF yielding 7,000 lbs.  This is a yield of 87.5% (7,000 lbs/ 8,000 lbs)

Some of item DEF (3,500 lbs) is used as ingredient for the item GHI yielding 3,000 lbs.  This is a yield of 85.7% (3,000 lbs/ 3,500 lsb).

Some of item GHI (1,000 lbs) is used as ingredient for the item JKL yielding 900 lbs.  This is a yield of 90.0% (900 lbs / 1,000 lbs).