DRIVE = 'Drive'
BIKE = 'Bike'
WALK = 'Walk'
KM_PER_HOUR_DRIVE = 50.0
KM_PER_HOUR_BIKE = 10.0
KM_PER_HOUR_WALK = 5.0
def trip_time(distance, vehicle):
"(float, str) -> float
Return the time it takes to travel the given distance using the given mode
"(list of list of str) -> dict of cfw_tuple of str: int
return dictionary where each key is a four-element tuple representing
the permutation and the value is the number of times that the permutation