1) Write mean_square (), a function that calculates and returns the mean (average) of the squares of the values in array. The function prototype is: double mean_square( double *a, int size ); For example: if the arguments were a = (1, 2, 3, 4), size = 4 then the return value would be - ( 12 + 2 + 32 + 42 ) / 4 = 7.50000 Assume all necessary header files are included. Do NOT write main(), do NOT print anything. 5 points