Using put–call parity a long butterfly can also be created as follows:
Long 1 put with a strike price of (X + a)
Short 2 puts with a strike price of X
Long 1 put with a strike price of (X − a)
where X = the spot price and a > 0.
All the options have the same expiration date.
At expiration the value (but not the profit) of the butterfly will be:
zero if the price of the underlying is below (X − a) or above (X + a)
positive if the price of the underlying is between (X - a) and (X + a)
The maximum value occurs at X (see diagram).
long put的时候需要premium吗?还是空手套白狼啊.
