Explanation : The price return of the index equals the weighted average of price returns
of the individual securities.
Return of A: −25 percent = (15 − 20)/20;
Return of B: 20 percent = (48 − 40)/40;
Return of C: 0 percent = (60 − 60)/60.
The price return index assigns equal weights to each asset; therefore, the
price return is 1/3 ∗ (−25% + 20% + 0%) = −1.7%.