The weights of oranges are normally distributed with mean 82 grams. 22% of these oranges have a weight greater than 87 grams. a) Find the standard deviation of the weights of these oranges. b) Find...

The weights of oranges are normally distributed with mean 82 grams. 22% of these oranges have a weight greater than 87 grams.
a) Find the standard deviation of the weights of these oranges.
b) Find the probability that the weight of a randomly chosen orange differs from the mean weight by less than 4 grams.