Jack owns a small coffee shop. He wants to know the average number of customers in his coffee shop, to decide whether he needs to add more space to accommodate more customers. Currently, his coffee shop can accommodate no more than eight customers. Jack measured that, on average, 40 customers arrive at his coffee shop every hour. He also determined that, on average, a customer spends around 6 minutes in his store. Given these inputs, Jack wants to know how many customers (on average) are in his coffee shop at any point in time.