Let the random variable z, represent the monthly return of a portfolio of commodities futures.

Let us denote the mean and variance of this random variable u and o^2 respectively. The monthly

commodity futures returns 2t are normally distributed; this can be denoted xt ~ N(4,03). Suppose

that the aforementioned portfolio has yielded the following returns over 17 consecutive months xt =

{1.2,0.3,2.1, -3.1,1.0,5.0, -0.8,1.4,3.8, 1.3,6.1, -3.5,2.9,1.9,0.7, -0.8,1.9%. How likely it is that the

portfolio yields a negative monthly return? Note: Please draw the necessary probability distribution graphs.

Use the CAMBRIDGE Statistical Tables