The world's largest $(19,000$ square feet$)$ McDonald's located in the heart of Orlando, Florida is open $24$ hours a day.$$ It has three floors and is close to Universal Studios and Walt Disney World.$$ Belgian Waffles, cheesecake, chocolate cake, dessert bar, brick oven pizza, or cheesesteak are part of its menu items. Build$-$your$-$own pasta and pizza dishes are included as well.$$ Suppose that at this McDonald's the average number of patrons served per unit time $($i$.$e$.,$ average service rate$)$ is Mu $($i$.$e$.,).$ Then, the average service time at this McDonald's is: