What would the number of units expected to be manufactured in March be?Production and sales estimates for March for the Robin Co. are as follows:...

The  company will need to manufacture 26,300
units in March.'

The reason for this is that
this is the sum of the number of units that they plan to sell in March plus the amount
that they wish to add to their inventory.

During the month,
they plan to sell 24,000 units over the three areas that you mention.  However, this is
not how many they plan to manufacture.  This is because they plan to have 2,300 more
units in their inventory at the end of the month than they had at the beginning. 
Therefore, they need to produce 2,300 more units than they
sell.

24,000 + 2,300 = 26,3000 and therefore
the answer is D.