A $20-$year, $7\%$ semi$-$annual coupon bond $($R$1000$ par value$)$ is priced at a yield to maturity of $12\%.$ The yield changes by $40$ basis points.

The duration effect if the yield is decreasing by $40$ basis is closest to $...$

a$.-3\mathrm{.}30\%$

b$.-8\mathrm{.}26\%$

c$.3\mathrm{.}30\%$

d$.8\mathrm{.}26\%$