Since jason is currently at 54 feet above sea level and David is 11 feet below sea level the add 11 plus 54 which would give you 65 feet is there distance of elevations
All you need to do is devide 300 by 50 because you know that you have 300 dolars and it is 50 dollars per person. 300/50 is 6 therefore 6 people can be at the party.