Write a function named cumulative that accepts as a parameter a reference to a vector of integers, and modifies it so that each element contains the cumulative sum of the elements up through that index. For example, if the vector passed contains {1,1,2,3,5}, your function should modify it to store {1,2, 4,7,12}. Write a function named mean that accepts as a parameter a reference to a vector of real numbers, and returns the arithmetic mean (average) of the integers in the vector as a real number. For example, if the vector passed contains {2.,4.5,6.5,1.}, your function should return 3.5. If the vector is empty, return .. Do not modify the vector that is passed in