Show that the payoff of long position in a straddle centered at strike K2 plus a loan for the present value of (K2 K1) is equal to a short position in a butterfly spread at strikes K1, K2 and K3 plus a strangle at strikes K1 and K3. Show that the payoff of long position in a straddle centered at strike K2 plus a loan for the present value of (K2 K1) is equal to a short position in a butterfly spread at strikes K1, K2 and K3 plus a strangle at strikes K1 and K3