Strategy - SELL STRADDLE (details below)
A call option and a put option are sold with the same strike price a.
Limied to the two premiums received - will be realised if market at expiry is exactly at the strike price level.
The lower point (b) will be the strike minus the value of two premiums received, the upper point (c) will be the strike plus the two premiums received. [If the investor would like to broaden this band, a sell strangle might be interesting].
Unlimited - should the market fall or rise greatly.
If the market does little then the value of the position will benefit as the short positions gain when the option time value falls.