Hi,

i am working one below challenge

http://codingbat.com/prob/p157900
i was not clear on below description

(A variation on the sumHeights problem.) We have an array of heights, representing the altitude along a walking trail. Given start/end indexes into the array, return the sum of the changes for a walk beginning at the start index and ending at the end index, however increases in height count double. For example, with the heights {5, 3, 6, 7, 2} and start=2, end=4 yields a sum of 1*2 + 5 = 7. The start end end index will both be valid indexes into the array with start <= end.

how below results are 7,2, 15 each? please advise

sumHeights2([5, 3, 6, 7, 2], 2, 4) → 7

sumHeights2([5, 3, 6, 7, 2], 0, 1) → 2

sumHeights2([5, 3, 6, 7, 2], 0, 4) → 15