The distribution of passenger vehicle speeds traveling on the Interstate 5 Freeway (1-5) in Washington is nearly normal with a mean of 57.2 miles/hour and a standard deviation of 6.3
miles/hour.
(a) What percent of passenger vehicles travel slower than 51 miles/hour?
(b) What percent of passenger vehicles travel between 48 and 67 miles/hour?
(c) The speeds that make up the middle 75% of all the speeds driven along this stretch of I-5 are from ___ to ___ miles/hour.
(d) What is the interquartile range of passenger vehicle speeds traveling on I-5 in California?