The daily surface concentration of carbonyl sulfide on the Indian Ocean is normally distributed, with a mean of 9.1 picomoles per liter and a standard deviation of 3.5 picomoles per liter. Find the probability that on a randomly selected day, the surface concentration of carbonyl sulfide on the Indian Ocean is

(a) between 5.1 and 15.7 picomoles per liter.

(b) between 10.5 and 12.3 picomoles per liter.

(c) more than 11.1 picomoles per liter.