Truliant Co$.$ sells a product called Withitall and has predicted the following sales for the first $4$ months of the current year:

$\backslash$table$[[,$January,February,March,April$],[$Sales in units,$1,700,1,900,2,100,1,600]]$

Ending inventory for each month should be $20\%$ of the next month's sales. How many units should be produced in February?

a$.1,850$

b$.1,940$

c$.1,800$

d$.1\mathrm{.}900$