Write a method that returns the "Jump Sum" of a list of numbers starting at 'lowest' and going up by 'jump' each time. Stop adding the numbers when you get above 'highest'. For example, the "Jump Sum" with lowest=4, highest=15, and jump=3 would be found by adding 4+7+10+13 which equals 34. Note that the "Jump Sum" would be the same if highest was changed to 13 or 14, but if highest was 16, the "Jump Sum" would now be 50. The value of 'jump' will always be positive.