Assume that only one client's order can be processed at any given point of time. So, Anish or Bani cannot start preparing a new order while a previous order is being prepared.
At what time is the ordre placed by Client 1 completely served?
10 : 10
Time to prepare one burger = 10 minutes
Time to prepare an ice-cream = 2 minutes
Time taken to serve first client completely = time taken in the preparation of a burger = 10 minutes
Hence, at 10:10 complete order will be served.