Answer:
Proportion y = 80%
Step-by-step explanation:
E(rc) - r(f) = y[E(rp) - r(f)]. Where E(rc) - r(f) is Risk premium of clients overall portfolio and y[E(rp) - r(f)] is Risk premium of clients risky portfolio
0.15 - 0.07 = y[0.17 - 0.07]
0.08 = y(0.10)
y = 0.08/0.10
y = 0.80
y = 80%
So, the proportion of risky portfolio(y) is 80%. So, to achieve overall return of 15% on portfolio, investors needs to invest 80% investment in risky portfolio.