Classify each of the following as being primarily a fixed cost or a variable cost, and, if necessary, explain why you think such a classification would be difficult without more information being provided

(a) direct materials;

(b) factory insurance;

(c) production manager's salary;

(d) advertising of the product;

(e) direct labour;

(f) indirect labour;

(g) depreciation of machinery;

(h) lubricants for machines;

(i) payment of a licence fee for the right to exclusive manufacture; and

(j) canteen manager's salary.