there are 85 flags paiges flag collection these 30 flags include red flags designs35

There are 85 flags in Paiges flag collection. Of these 30 of the flags include red in the flags designs,35 include white and 24 include neither red nor white. What is the number of flags in Paiges collection that MUST include both red and white? the answers are a.0 b.1 c.2 d.4