Which statement$($s$)$ about the Newsvendor model are true? Select all that apply.

The optimal service level should be set equal to fraction numerator C u over denominator C u plus C o end fraction.

The main tradeoff is between cost of over$-$ordering and cost of under$-$ordering.

It is applicable when demand is uncertain and supply decision has to be made ahead of time.

The main tradeoff is between inventory holding cost and fixed ordering cost.