Question 1147613
z=(x-mean)/sd
>(x-12.4)/20.6
>(0-12.4)/20.6
>-0.60
That probability is 0.7258

more than 10% return
z>(10-12.4)/20.6
>0.12
That probability is 0.4522

10%ile is z=-1.28
That value is -1.28=(x-mean)/20.6 or -26.64=x-12.4 or x=-14.24 per cent
10% or the returns are below the tenth percentile; 90 per cent are above it.