Find the first and last names of people who payed more than the rooms' base prices.
SELECT T1.firstname ,  T1.lastname FROM Reservations AS T1 JOIN Rooms AS T2 ON T1.Room  =  T2.RoomId WHERE T1.Rate - T2.basePrice  >  0
first and last names refer to firstname, lastname; paid more than rooms' base prices refers to Rate - basePrice > 0; joining tables Reservations and Rooms to compare rates and prices.