Answer:
a. Amount to invest in Y
The amount that will be invested in Stock Y should be such that the expected return of the portfolio would equal 12.1%.
This would be determined by the weights of the stock.
Assume the weight to be invested in X is x.
Portfolio return = (weight of X * Return of X) + (weight of Y * Return of Y)
12.1% = (x * 10.28%) + ( (1 - x) * 7.52%)
0.121 = 0.1028x + 0.0752 - 0.0752x
0.121 - 0.0752 = 0.1028x - 0.0752x
0.0458 = 0.0276x
x = 0.0458 / 0.0276
= 1.6594
Weight in stock Y:
= 1 - 1.6594
= -0.6594
Amount to invest in Y:
= -0.6594 * 100,000
= -$65,940
b. Portfolio beta
It will be a weighted average of the betas of the two stocks:
= (Weight of stock X * Stock X Beta) + ( Weight of stock Y * Stock Y beta)
= (1.6594 * 1.20) + (-0.6594 * 0.80)
= 1.46