The following table indicates the average total cost of producing varying quanti ties of output from three different plants: Rate of output 10    20    30     40     50     60     70     80       90       100 Average total cost Small firm  $ 600 $500 $400 $500 $600 $700 $800 $900 $1,000 $1,100 Medium firm 800   650   500   350   200   300   400   500     600      700 Large firm  1,000   900   800   700   600   500   400   300     400      500 ( a ) Plot the ATC curves for all three firms on the graph

The following table indicates the average total cost of producing varying quanti ties of output

from three different plants:

Rate of output 10    20    30     40     50     60     70     80       90       100

Average total cost

Small firm  $ 600 $500 $400 $500 $600 $700 $800 $900 $1,000 $1,100

Medium firm 800   650   500   350   200   300   400   500     600      700

Large firm  1,000   900   800   700   600   500   400   300     400      500

( a ) Plot the ATC curves for all three firms on the graph.

( b ) Which plant(s) should be used to produce 40 units?

( c ) Which plant(s) should be used to produce 100 units?

( d ) Are there economies of scale in these plant size choices?