An aggregate planner is facing the forecasted demand below. She cannot possess any inventory at the end of any period during this planning horizon, but must use a level strategy and subcontracting to meet demand. Assuming that subcontracted units are more expensive than in$-$house units and keeping her constraints in mind, what would be the most appropriate level monthly production amount?

$\backslash$table$[[$Period$,1,2,3,4],[$Demand$,1000,1100,1300,1400]]$

$1000$ units

$1100$ units

$1200$ units

$1400$ units