Which of the following is a true statement about the carriable overhead efficiency variance when the allocation base is direct labor hours?

a$.$ It tells whether one paid more or less than planned for variable overhead resources.

b$.$ It is correlated with the direct labor efficiency variance since overhead is applied based on direct labor hours.

c$.$ Part of information used to calculate it can also be used to determine the direct labor rate variance.

d$.$ It tells you whether one was efficient or not in the use of variable overhead resources,