An inventory system answers two important questions: when to order and how much to order. Which of the following statements correctly explains how a Q$,$R system $($continuous review system$)$ answers these questions?

Under a Q$,$R rule, a fixed quantity is ordered every T time periods.

Under a Q$,$R rule, a fixed quantity Q is ordered when the inventory position reaches the order point R$.$

under the Q$,$ R rule, an order is placed once every $T$ periods for an amount equaling the difference between current position and a desired inventory level $)$ on receipt of the replenishment order.

$$ None of the options is$.$correct