a) There are 7 identical bags. In each bag, there are 9 balls, numbered from 1 to 9, inclusive. We randomly pick a ball from each bag. Determine the probability that product of the 7 number on the 7 balls is a multiple of 3. You do not need to simplify your answer. b) Assuming 105 bits are independently transmitted over a network in which the probability of an erroneous bit is 10-5, calculate the probability of bit error when the total number of errors is less than or equal to 5. You do not need to simplify your answer.