Resset co. provides the following results of April's operations: F indicates favorable and U indicates unfavorable. Applying the management by exception approach, which of the variances are of greatest concern? why?

Direct materials price variance: 300 F

Direct materials quantity variance: 3.000 U

Direct labor rate variance: 100 U

Direct labor efficiency variance: 2.200 F

Controllable overhead variance: 400 U

Fixed overhead volume variance: 500 F