Correct structure of the sentence would be as follows to offer parallelsim
The yield is expected to X and to Y
( Infact second "to" could be optional)
Hint. items around "and" must be parallel
Only A and B qualify
Also, clearly...6 billion cubic feet a day is a rate hence....", an extraction rate" would be perfect match
In A
6 billion cubic feet a day, which will allow such an extraction rate....
which ideally refers to the noun that precedes --I think we cannot separate "6 B cubic feet " and "a day" as they are a single unit hence which refers to "6 B cubic a day"
hence sentence means "rate will allow such an extraction rate"..
clearly meaning is lost