Spex Appeal Inc. has the following direct labor standard to manufacture one pair of eyeglasses: $1\mathrm{.}5$ standard hours per eyeglasses at $$12\mathrm{.}00$ per direct labor hour. $1,550$ direct labor hours were actually worked at a total labor cost of $$18,910$ to make $1,000$ eyeglasses.

Spex's labor efficiency variance was:

$$590$ U

$$590F$

$$600U$

$$600F$