( Average total cost) = ( average fixed cost) + ( average vairable cost)
totalcost quantity \frac{\;\text{totalcost}\;}{\;\text{quantity}\;}quantitytotalcost + (total variable cost) quantity \frac{\;\text{(total variable cost)}\;}{\;\text{quantity}\;}quantity(total variable cost)
\frac{}{}600}{100}+++\frac{400100400{100}400100
= \6+6 + \\6+4 = \$10
