Answer:
units 10000
contribution per unit = $20
sales per unit(price)= $60
we know that, variable cost= sales - contribution
1 method--
variable cost= $60 - $20
= $40 per unit
variable cost = 10000 units *$ 40
= $400000
2nd way----
contribution = 10000 units * $20
= $200000
sales = 10000 units * $ 60
variable cost = $600000 - $200000
= $ 400000