There are four available investment funds. Their rates of return are all independent. How can you get the highest rate of return for the least risk? E[r_North] = 10%, StDev_North = 20%;

E[r_South] = 10%, StDev_South = 20%;

E[r_East] = 10%, StDev_East = 20%;

E[r_West] = 10%, StDev_West = 20%.