# File utilities/Flow.rb, line 18
  def apply(p,t)
    k1 = get(p)*t
    k2 = get(p + k1* 0.5)*t
    k3 = get(p + k2* 0.5)*t
    k4 = get(p + k3)*t

    k2.times(2)
    k3.times(2)
    k1.add(k2)
    k1.add(k3)
    k1.add(k4)
    k1.times(1/6.0)
    k1.add p
    return (k1)
  end