An Office Manager uses a Periodic Review Inventory System: they check the inventory in the Office Supply Closet once every $10$ days, placing an order with their supplier depending on the inventory level in the closet. Once the order is placed, it takes $3$ days to receive the order. The average demand for post it notes is $30$ per day. This week, the manager has counted $140$ post it notes in the closet.

What is the Minimum Restocking Level $($restocking policy$)$ needed to cover expected demand over time without stocking out?