7. Consider the following data matrix. Each row is a sample from a random vector x e R4. 8 3 84 6 21 9 U 9 5 U 102 3 2 6 4 2 X = 5 8 35 6 l5 1 54 3 8 7 14 5 3 1 50 14 17 1 92 4 a) What is the mean of x? b) What dimensions does the sample covariance matrix of K have? c) Compute the sample covariance matrix of x {please show your work; you are allowed to use a computer but onlyr for basic matrix operations like matrix multiplication)