def cost(distance):
    """
    Calculates the cost to run a trip. Returns a float.

    July 21, 2020: $0.89/L of fuel in NYC 
    Fuel Efficiency (Avg Estimate): 9.4L/100 km  

    c(x) = price * ((distance * price)/fuel efficiency)
    ==Parameters==
    distance: distance in metres 
    """
    d = distance/1000
    price = 0.89
    fuel_e = 9.4

    amount = (d * price)/fuel_e
    return price * amount