If unit cost varies with volume of activity, such cost is known as : a. Variable Cost b. Fixed Cost

Fixed Cost as it is multiflied by the volume of activity

b. Fixed Cost

fixed cost per unit will change as the level of volume or activity changes

variable cost fixed cost remain constant but it increase is case of increasing the relevant range 

it is variable Cost

VARIABLE cost

Fixed cost, of course

variable cost

Its Fixed Cost. Because the unit cost varies in accordance with Total Volume of the activity.