Please answer question 18 with all steps

TABLE 7.6 Standard deviations of returns and correlation coefficients for a sample of seven stocks Note: Correlations and standard deviations were calculated using returns in each country's own currency. In other words, they assume that the investor is protected against exchange risk. 18. Portfolio risk (S7.4) Your eccentric Aunt Claudia has left you $50,000 in BP shares plus $50,000 cash. Unfortunately, her will requires that the BP stock not be sold for one year and the $50,000 cash must be entirely invested in one of the stocks shown in Table 7.6. What is the safest attainable portfolio under these restrictions