// EFFECTS: adds the next element in the list to the sum so far int TailRecursiveSumHelper(RecursiveList list, int sum_so_far) { // Implement this function. return 0; } // EFFECTS: returns the sum of each element in list, or zero if the list is // empty // THIS FUNCTION IS PROVIDED AS PART OF THE STARTER CODE. // DO NOT MODIFY THIS FUNCTION. int TailRecursiveSum(RecursiveList list) { return TailRecursiveSumHelper(list, 0); }