The weights of an orange in the bin at the grocery store vary normally with a mean of 10 oz. and a standard deviation of 2.5 oz. If you randomly pick two oranges out of the bin, what is the probability that the difference in their weight is at least 1 oz? a) 0.421
b) 0.389
c) 0.778
d) 0.135
e) 0.842