Thickness measurements of ancient prehistoric native american pot shards discovered in a hopi village were approximately normally distributed with a mean of 5.1 mm and a standard deviation of 0.9 mm. for a randomly found shard, what is the probability that the thickness is
(a) less than 3.0 mm
(b) more than 7.0 mm
(c) between 3.0 and 7.0 mm