Variable cost:
A cost that changes, in total dollar amount, with the change in the level of activity is called variable cost. A common example of variable cost is direct materials cost. Consider the following example to understand how variable cost behaves in a manufacturing company.
A mobile phone manufacturing company purchases speakers from another company at a cost of $2 per speaker. The speaker is a direct materials cost for mobile phone manufacturing company. One speaker is used to complete a mobile phone. The total and per unit cost of speakers at various levels of activity is given below: