Determination of the additional profits:
1) The new investment gets a certain share 
of the increase in total profits in the
economy (determined by the same investment!),
a share only because owing to imperfect
competition and existing ? capacity, the existing old equipment
will absorb a share of the new ? sales +
therefore profits, and probably the major share!
Thus I_(II)=n?P
                II   
You see here how he is supposed
to calculate!

2)