Longview Hospital performs blood tests in its laboratory. The following standards have been set for each blood test performed: During May, the laboratory performed 1,500 blood tests. On May 1 there were no direct materials (plates) on hand; after a plate is used for a blood test it is discarded. Variable overhead is assigned to blood tests on the basis of direct labor hours. The following events occurred during May:

STANDARD QUAMTITY OR HOURS                           STANDARD PRICE OR RATE

DIRECT MATIERALS                                                                                          2.0 PLATES                                                                       $2.75 PER PLATE

DIRECT LABOR                                                                                                 0.2 HOURS                                                                       $15.00 PER HOUR

VARIABLE OVERHEAD                                                                                    0.2 HOURS                                                                         $7.00 PER HOUR

· 3,600 plates were purchased for $9,540

· 3,200 plates were used for blood tests

· 340 actual direct labor hours were worked at a cost of $5,550

The labor efficiency variance for May is: