Bond Q is a $4$ percent coupon bond. Bond R is a $6$ percent coupon bond. Both bonds have $15$years to maturity, make annual coupon payments, and have a YTM of $6$ percent. If interest rate $($YTM$)$ changes from $6$ percent to $8$ percent, what is the percentage price change of these bonds? What if the YTM suddenly falls from $6$ percent to $4$ percent instead? What does this problem tell you about the interest rate risk of lower$-$coupon bonds?