Tannwin Co Ending Inventory for Each Month Should Be 20% of the Predicted

Multiple Choice

Tannwin Co. sells a new product called Accountomatic and has predicted the following sales for the first four months of the current year:
$$\begin{array} { c c c c c } & \text { Jan. } & \text { Feb. } & \text { March } & \text { April } \\\text { Sales in units } & 1,700 & 1,900 & 2,100 & 1,600\end{array}$$
Ending inventory for each month should be 20% of the next month's sales, and the December 31 inventory is consistent with that policy. How many units should be purchased in the first quarter of the year?

A) 5,100
B) 5,680
C) 6,300
D) 6,000
E) 5,700