Problem 44467. Product of Each Column

Given a matrix mat with n columns, return a row vector v of length n, where every element in v is the product of the n-th column.

You cannot use MATLAB Prod() function

Example:

Input: mat = [ 1,  2,  3,  4;
               5,  6,  7,  2;
               2,  3,  4,  5]
Output: v  = [10, 36, 84, 40]