count if the product of one column minus another column is >=91

[VADER73]

Column A contains dates. Column B also contains dates but each corresponding cell is a later date than Column A. Column C contains team identification codes e.g. AT521.

I am having difficulty producing an array formula that will count if Column C equals team code AT521 AND Column B subtracted from Column A is greater than or equal to 91 days.

I would appreciate any help.

 

[Scott Huish]

=sumproduct(--(c1:c100="at521"),--(b1:b100-a1:a100>=91))

 

[VADER73]

=sumproduct(--(c1:c100="at521"),--(b1:b100-a1:a100>=91))

Thank you very much for your help. Worked perfectly.