Pin Drop Technologies Inc. manufactures and assembles mobile phones in a just-in-time cell. The company budgeted for 1,200 phones for the month. Conversion costs for 1,200 units were applied to the phone assemblies at a conversion cost of $12 per unit. Only 1.150 mobile phones were completed and moved to the finished goods storeroom by the end of the month. Using just-in-time costing, the cell efficiency variance would be O $ 600 unfavorable O $0 O $ 600 favorable O $ 13,800 favorable