A Fair coin is tossed 3 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
a: P(not A)
b: P(B or (not C))
c: P(A or B or C)