Indicate whether each of the following matrices is a valid variance-covariance matrix for the three assets A, B, and C. For all cases, write down the reason why the matrix is or is not a valid variance-covariance matrix. No marks without full and detailed justification. (2.5 marks each).

1

1.99	-0.05	-0.11
-0.05	2.99	-0.02
-0.11	-0.02	-3.62

2

0.12	0.03	1.06
0.03	0.09	0.12
1.06	0.12	0.04

3

0.92	0.03	0.18
0.03	0.04	0.14
0.08	0.14	0.08

4

4.18	0.08	0.22
0.08	0.14	0.14
0.22	0.14	0.08