Parker Plastic, incorporated, manufactures plastic mats to use with roling office chairs. its standard cost information for last year follows: Parker Plastic had the following actual results for the past year: Required: Calculate Parker Plastic's variable overhead rate and efficlency variances and its over-or underapplied variable overhead. Note: Do not round intermediate calculations. Indicate the effect of each variance by selecting "F" for favorable, "U" for unfavorable, and "None" for no effect (i.e., zero variance)