Your question is Linq, WCF, And Reservation Design. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Explain how you would design a railway reservation system by extending a current airline design, and walk through the key differences between LINQ Select and Where, plus how you would disable lazy loading and throttling in WCF.