Let A be the family of closed intervals that contains 0 and are contained in (-1,1). Thus I is in A if and only if I = [a,b], where -1<a<0<b<1. Determine the following sets and justify you answers:

(a) $\displaystyle \bigcup_{I \epsilon A} I $

(b) $\displaystyle \bigcap_{I \epsilon A} I $