Given function trace defined below note: ones is a built-in function. ones(n) returns a n by n matrix with components of 1. function a = trace(A) [lengthx, lengthy] = size(A); a = 0; for i = 1: lengthx a = a + A(i,i); end end What is the value of a if you execute the following code A = ones(15)*2; a = trace(A) B) a=30 A) a=15 C) a=40 D) a=60 E) Error uting the following code