Suppose there are seven firms in a market where the three largest firms supply $20\%$ of the market$-$clearing quantity and the other four firms supply $10\%$ of the market$-$clearing quantity. What is the five$-$firm concentration ratio $($i$.$e$.,$ the share of total sales controlled by the five largest firms in the market$)?$

A$)60\%$

B$)70\%$

C$)80\%$

D$)90\%$

Answer: C