(a) Assume that $P(A)=0.4, P(B)=0.3$, and $P(C)=0.1$. If the events $A, B$, and $C$ are disjoint, find the probability that the union of these events occurs.
(b) Draw a Venn diagram to illustrate your answer to part (a).
(c) Find the probability of the complement of the union of $A, B$, and $C$.