Suppose you wish to predict production yield y as a function of several independent predictor variables. Indicate whether each of the following independent variables is qualitative or quantitative. If qualitative, define the appropriate dummy variable(s).
a. The prevailing interest rate in the area
b. The price per pound of one item used in the production process
c. The plant (A, B, or C) at which the production yield is measured
d. The length of time that the production machine has been in operation
e. The shift (night or day) in which the yield is measured