At the highest level of activity in November, total cost is $$125,000,$ and the units produced are $2,500.$ At the lowest level of activity in August, total cost is $$80,000,$ and the units produced are $1,000.$ Applying the high$-$low method, the estimated unit variable cost is

A$)$ $$30$

B$)$ $$50$

C$)$ $$80$

D$)$ $$130$

E$)$ none of the above