Answer: 4.86%
Explanation:
The Capital Asset Pricing Model can be used;
Return = Risk free rate + beta * ( market return - risk free rate)
10.5% = Rf + 1.55 * (8.5% - Rf)
10.5% = Rf + 0.13175 - 1.55Rf
10.5% - 0.13175 = -0.55Rf
-0.02675 = -0.55Rf
Rf = -0.02675/-0.55
= 0.0486
= 4.86%