The true weight of "10-pound" sacks of potatoes processed at a certain packaging house follows a normal distribution with mean of 10.1 pounds and standard deviation of 0.2 pounds.
a) What is the probability that a sack weighs at least 10 pounds?
b) A random sample of 9 sacks is selected. What is the probability that the average weight of these 9 is at least 10 pounds?