y = (x * Y * X) / (x + X)^2
, where x = input, X = Input Asset, Y = Output Asset, y = output
fee = ( x^2 * Y ) / ( x + X )^2
stakeUnits = ((R + T) * (r * T + R * t))/(4 * R * T)
, where r = SXP Staked, R = SXP Balance, T = Token Balance, t = Token Staked