Task: Question Generation
Input (English): #1 return flights 
#2 return #1 from dallas 
#3 return #2 to  baltimore 
#4 return #3 on december seventeenth 
#5 return price of #4 
#6 return #4 where #5 is  the  lowest
Output (English): what's the cheapest flight from dallas to baltimore on december seventeenth