The following data give the number of hours worked last week by 18 randomly selected managers working for various Wall Street financial companies.

45     54     63     79     48     50     49     52     74
61     55     56     58     56     77     66     64     70

a. Calculate the three quartiles and the interquartile range. Where does the value of 54 lie in relation to these quartiles?
b. Find the (approximate) value of the 60th percentile. Give a brief interpretation of this value.
c. Calculate the percentile rank of 64. Give a brief interpretation of this value.