Question 1179383
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You should find the value of x from the break-even equation


    C(x) = R(x),


which is


    84x + 2160 = 108x.


The solution is  x = {{{2160/(108 - 84)}}} = 90.


<U>ANSWER</U>.  The number of units is 90.
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Solved, answered and explained.  And completed.