% description X=sigma=volatility
function fun=f(x)
K=1180;
S0=1092.34;
r=0.0075;
T=3/12;
c=14.625;
d1=(log(S0/K)+(r+(x*x./2)*T))./(x*sqrt(T));
d2=d1-x*sqrt(T);
fun=S0*cndf(d1)-K*exp(-r*T)*cndf(d2)-c;
