To keep in shape, ellie exercises at a track near her home.
she requires 36 minutes to do 4 laps running and 4 laps walking.
in contrast, she requires 63 minutes to do 9 laps running and 6 laps walking.
assuming she maintains a consistent pace while running and while walking, how long does ellie take to complete a lap?
Ellie takes _______ minutes to run a lap and _____minutes to walk a lap.