In a continuous review. $(R,Q)$ inventory management system what do the values of $R$ and $Q$ define?

Place order every $Q$ time periods to bring the inventory level up to $R.$

$Q$ is the on$-$hand inventory whereas $R$ is the on$-$order iriventory.

Whenever inventory drops to reorder point, R$,$ the system orders quantity, $Q.$

Whenever inventory drops to trigger quantity, $Q,$ the system orders a reolenishment amount, R$.$

$Q$ is the quantity ordered with constant demand, $R$ is the quantity ordered with uncertain demand.