The answer is (usted) because you dont have a personal relationship with this person.
ustedes means you guys
vosotros means all of us
tu is used for someone whom you are close with like a family member or someone whom you have know for a while.
Traje de bano
because it is talking about the beach and traje de bano is a bathing suit.
botas is boots
abrigo is a coat
blusa is a blouse
