7 . Due to the similarity of the equipment in each of the production stages and the company's concentration on a single product , manufacturing overhead is allocated based on volume ( i.e. the units produced ) . The unit variable overhead manufacturing rate is $1. 30 , consisting of : Utilities - - $0 . 60; Indirect Materials - - $0. 20; Plant maintenance - - $0. 30; environmental fee - - $0 . 14 ; and Other - - $0. 06