The following prices are observed in the market for an option: (all options are on the same underlying with same maturity time)
Stock trades at S0 = 100
A straddle with K=100 trades at 7.9
A strip with K=100 trades at 12.1
A strap with K=100 trades at 11.6
A strangle with K1=95 and K2=105 trades at 5.0
A butterfly spread with K1=95, K=100 and K2=105 trades at 2.1
Describe a risk-free strategy to make money in this market (only trading the above instruments)