in C++

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 {2.0, 4.5, 6.5, 1.0}, your function should return 3.5. If the vector is empty, return 0.0. Do not modify the vector that is passed in.

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}.