Answer:
the expected returns are missing, so I looked for a similar question:
Treasury bills  4.5%  $80,000
Ford (F) 8.0% Â $60,000
Harley Davidson (HOG) 12.0% Â $60,000
a) portfolio's expected return = (4.5% x $80,000) + (8% x $60,000) + (12% x $60,000) = $15,600
b) new portfolios expected return = (8% x $100,000) + (12% x $100,000) = $22,000
c) to lower risk. Treasury bills pay a low return but they are risk free investments. While stocks yield a higher return but they also carry a much higher risk.