Can you find the first and last names of all people who paid less 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
people who paid less than rooms' base prices refers to comparison between T1.Rate and T2.basePrice; first and last names refer to firstname and lastname fields respectively; need to join Reservations and Rooms tables on Room/RoomId;