E$.$ impossible to say without more information

$6.$ A firm has $56$ units of product $x$ on hand. Forecasts of demand are for $20$ units per week. An MPS quantity of $100$ units is planned to arrive in period $3.$ Customer orders are $24$ for period $1,18$ for period $2,15$ for period $3.$ What quantity is available for commitment to new customers prior to the receipt of the MPS quantity in week $3?$

A$.14$

B$.32$

C$.12$

D$.20$

E$.$ impossible to say without more information