If Sentence – Type 3 (If + past perfect + would have)

Three-letter word beginning with “h”.

Four-lettered word beginning with “h”.

First word begins with “g” and has four letters. The second word begins with “w” and has five letters. The last word has two letters starting with “b”.

The first word begins with “h” and has three letters. The second begins with “w” and has five letters. The third begins with “b” and has two letters.

“been” goes in the second and last gap.  Forms of “have” go in the first and third gap.

The first word is the past tense of “have”.  The second word is “would”.  The last one is a form of “have”.  Which form of have follows “would”?