An $8-$year, $10\%$ semi$-$annual coupon bond $($R$1000$ par value$)$ is priced at a yield to maturity of $7\%.$ The yield changes by $125$ basis points. What is the convexity and convexity effect of the bond respectively?

a$.18\mathrm{.}21,0\mathrm{.}01\%$

b$.20\mathrm{.}840\mathrm{.}33\%$

c$.20\mathrm{.}840\mathrm{.}37\%$

d$.18\mathrm{.}210\mathrm{.}65\%$