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: