question: what is the cheapest round trip coach flight between dallas and baltimore leaving august tenth 
#1 return flights 
#2 return #1 that  are round trip 
#3 return #2 in coach 
#4 return #3 between dallas 
#5 return #4 and  baltimore 
#6 return #5 leaving august tenth 
#7 return #6 that  is  the cheapest