Answer:
see below
Explanation:
Las
because when you say "las", you are saying that Mercedes y tu compraron faldas (you and Mercedes bought skirts
A, B, or D can be correct it depends what date would be wanted
First ¿Cuánto Cuesta? means How much in Spanish to answer correctly to that answer you say a number for an example:
Girl : ¿Cuánto Cuesta?
Guy: Tres
you may saw the object you are talking about.
But if you wan to answer as saying in terms like how much you love someone you say todo esto which means this much.