Rebecca voluntarily decides to buy a dress that Hillary has for sale; they agree on a price of $20. Which of the following best describes who gains and who loses from the transaction?

A. If the dress originally costs less than $20, Hillary gains and Rebecca loses.

B. Both parties expect to gain from this transaction.

C. If the dress originally costs more than $20, Rebecca gains and Hillary loses.

D. If Hillary gains from the transaction, Rebecca must lose an equal amount.

I dont know if its B or C