transportTime

(defun transportTime (inputDistance) ; in km
    (defun divideAndPrint (input divisor methodOfTransport)
        (let timeTaken (/ inputDistance divisor)
            (list 'string
                "The distance is "
                (write-to-string timeTaken)
                " away by "
                methodOfTransport
                ", using an average speed of "
                (write-to-string divisor)
                " km/h.")))
    (if (< inputDistance 0)
        nil
    (if (< inputDistance 150)
        (divideAndPrint inputDistance 50 "car") ; cars, 50 km/h
    (if (< inputDistance 2500)
        (divideAndPrint inputDistance 130 "train") ; trains, 130 km/h
    (if (< inputDistance 12500)
        (divideAndPrint inputDistance 800 "plane") ; planes, 800 km/h
        (divideAndPrint inputDistance 18000 "ICBM")))))) ; ICBMs, 18000 km/h