Determine whether the following are valid probability models or not. Type "VALID" if it is valid, or type "INVALID" if it is not.

(a)

Event	$e_1$	$e_2$	$e_3$	$e_4$
Probability	$0.1$	$0.2$	$0.7$	$0$

Answer:

(b)

Event	$e_1$	$e_2$	$e_3$	$e_4$
Probability	$0.2$	$0.2$	$-0.2$	$0.8$

Answer: