Answer:
(B) $18.40
Step-by-step explanation:
we build the equation system and solve for variable overhead
we must understand that overhead unit cost if calculate as follow:
variable overhead + fixed overhead / volume
so:

We rearrange:

We equalize:

And now we solve:
(33.8 - VMO) x 3 = 64.6 - VMO
101.4 - 3 VMO = 64.6 - VMO
36.8 = 2VMO = 18.4