3. Create the following matrix A A = 4 5 6 7 1 2 3 246 21 18 15 8 10 12 14 12 9 6 3 5 10 15 20 25 30 35 (a) Create a 3 x 4 matrix called B from the first, third and fourth rows, and the first, third, fifth and seventh columns of the Matrix A. (b) Create a fifteen-element row vector named U from the elements of the third row, and the fifth and seventh columns of the matrix A. (10 marks)