David lives in Miami and is going to Dallas to meet a client for his marina business. David can take a cab from home for $$50$ roundtrip. A cab costs $$20+$ $$5($$$1$ airport fee and $$4$ as a $20\%$ tip each way$),$ Alternatively David can drive and park his car at Miami International Airport for $$20$ per night. For a one$-$day trip by cab, it would cost David $$50$ by cab vs$.$ $$20$ to park. For a two$-$day trip, it would cost $$50$ for a cab and $$40$ to park. For a three$-$day trip, it would cost $$50$ for a cab and $$60$ to park. For additional days, the cab is $$50$ and the parking $$20$ x the number of days. For trips of what length is it cost$-$efficient for David to drive and park vs$.$ take a cab?