Among the 30 largest U.S. cities, the mean one-way commute time to work is 25.8 minutes. The longest one-way travel time is in New York City, where the mean time is 39.7 minutes. Assume the distribution of travel times in New York City follows the normal probability distribution and the standard deviation is 7.5 minutes.

a. What percent of the New York City commutes are for less than 30 minutes?

b. What percent are between 30 and 35 minutes?

c. What percent are between 30 and 50 minutes?