You put half of your money in a stock portfolio that has an expected return of 28% and a standard deviation of 24%. You put the rest of your money in a risky bond portfolio that has an expected return of 7.5% and a standard deviation of 12%. The stock and bond portfolios have a correlation of .55. The standard deviation of the resulting portfolio will be ________.

Select one:

a.more than 12% but less than 18%

b.more than 18% but less than 24%

c.equal to 18%

d.equal to 12%

I think I'm not plugging number in formula right way. I am struggling to figure this out .