Portfolio A consists of a one$-$year zero$-$coupon bond with a face value of R$2000$ and a $10-$year zero$-$coupon bond with a face value of R$6000.$ Portfolio B consists of a $5\mathrm{.}95-$year zero$-$coupon bond with a face value of R$5000.$ The value of Portfolio A is R$4016\mathrm{.}95$ and the value of Portfolio B is R$2757\mathrm{.}81.$ The current yield on all bonds is $10\%$ per annum. The values of Portfolio A and Portfolio B with a $6\%$ increase in the yield is R$2915\mathrm{.}67$ and R$1929\mathrm{.}84$ respectively. Calculate the percentage reduction in the values of Portfolio A and Portfolio B when the yield increases by $6\%$ per annum. $(2)$