EliCo sells widgets. Daily demand for widgets is normally distributed with a mean of $100$ and a standard deviation of $10.$ When widgets are ordered from the supplier it takes $9$ days for the order to arrive.

Suppose EliCo reorders widgets when the inventory in the warehouse hits reorder quantity $R=900.$ What is EliCo's service level?

$33\mathrm{.}3\%$

$44\%$

$66\%$

$60\%$

$50\%$

$90\%$

$10\%$