Average total cost (dollars per scooter) 
Q = 50 Q = 100 Q = 150 Q = 200 Q = 250 Q = 300 
1 220 140 120 160 240 400 
2 310 190 120 120 190 310 
3 400 240 160 120 140 220 
Which quantity (Q) corresponds to the minimum average total cost per scooter? 
a) 50 
b) 100 
c) 150 
d) 200