#Note: due to 64 bit floating point limitations, do not call with N>60
function binomEU(S,K,T,r,sigma,N)
  if N>60
    error("USE N<60")
  end
  dt = T/N
  U = exp((r  - (sigma^2)/2)*dt + sigma*(dt^.5))
  D = exp((r  - (sigma^2)/2)*dt - sigma*(dt^.5))
  R = exp(r*dt)
  P = (R-D)/(U-D)
  period = Array{Float64}(N)
  for i in 1:N
    period[i] = binomial(N,i) * P^i *(1-P)^(N-i) * max(U^i * D^(N-i) *S - K,0)
  end
  C = (1/R^N)*sum(period)
  P = C - (S - K*R^(-N))
  return C,P
end