How about if we try an EXAMPLE of MR=MC for a perfectly competitive firm?
Answer the next question on the basis of the following information for a purely competitive firm:
Output------------Price------------Total Cost
----0--------------$100---------------$100
----1--------------$100---------------$260
----2--------------$100---------------$290
----3--------------$100---------------$350
----4--------------$100---------------$480
----5--------------$100---------------$700
How many units would the above profit-maximizing firm produce?