(defn taxi-fare [milesTraveled, pickupTime]
  (let [
       baseFare 2.50
       costPerMile 2.00
       nightSurcharge 0.50
       cost (+ baseFare (* costPerMile milesTraveled))]
       (if (or (<= pickupTime 6)
               (<= 20 pickupTime))
           (+ nightSurcharge cost)
           cost)))