How I calculated the answer for #5 in the FIN442 Homework: Given that we knew the risky portfolio's ?, expected return, the risk free asset's return, and additionally the ? for the total portfolio we would then setup a table of portfolio weights and use the formula on pp. 172 of our textbook. It looks like this:

			total sd	20%
		Standard Dev	Expected Return
Risky	x1	25%	12%
Risk Free	x2	0%	7%
	x1	0	0.25	0.5	0.75	0.8	1
	x2	1	0.75	0.5	0.25	0.2	0
	ex return	7%	8%	10%	11%	11%	12%
					19%	20%	12%