A fair coin is tossed three times and the events $A$, $B$, and $C$ are defined as follows:

$A: \{$ At least one head is observed $\}$
$B: \{$ At least two heads are observed $\}$
$C: \{$ The number of heads observed is odd $\}$

Find the following probabilities by summing the probabilities of the appropriate sample points (note that 0 is an even number):

(a) $P(B)$ $=$
(b) $P(A \textrm{ or } (\textrm{not }B))$ $=$
(c) $P(A \textrm{ or } B \textrm{ or } C)$ $=$