Classify each of the following as nominal, ordinal, interval, or ratio data.
a. The time required to produce each tire on an assembly line
b. The number of quarts of milk a family drinks in a month
c. The ranking of four machines in your plant after they have been designated as excellent, good, satisfactory, and poor
d. The telephone area code of clients in the United States
e. The age of each of your employees
f. The dollar sales at the local pizza shop each month
g. An employee's identification number
h. The response time of an emergency unit