$\backslash$table$[[$Firm$,\backslash$table$[[$Industry $1],[$Output$]],\backslash$table$[[$Industry $2],[$Output$]],\backslash$table$[[$Industry $3],[$Output$]]],[$Firm A$,100,100,20],[$Firm B$,0,100,20],[$Firm C$,0,100,20],[$Firm D$,0,0,20],[$All other firms,$0,0,1000]]$

Instructions: Round your answers to two decimal places.

a$.$ Calculate the four$-$firm concentration ratio for Industry $1.$

Industry $1$: $\%$

b$.$ Based on the information provided, what market structure best characterizes Indust

Industry $1$ :