For a manufacturer, measures of volume may include:
(a) number of square feet occupied.
(b) amount of direct materials used in production.
(c) number of units produced.
(d) both number of units produced and amount of direct materials used in production are correct.

(D) Both number of units produced and amount of direct materials used in production are correct.

Explanation:

"D"

Explanation:

Volume can mean  many thing to different categories of items.While  in book it means part of a series , in manufacturing it is the degree of space occupied.

As a lot of objects ,materials ,items , machinery ,manpower and other physical assets  are involved in manufacturing process , which definitely occupies spaces. The area of the spaces occupied by any of these group of items is measured in volume as long as it is of a particular height.

Formula is Length * breadth*height

answer/// product differentiation;