A copper wire has a resistance of $25\mathrm{m}\mathrm{\Omega }$ at ${20}^{\prime }\mathrm{C}$ When the wire is carrying current, heat produce by the current causes it's temperature to increase by ${27}^{\circ }\mathrm{C}$. What is the change in the wire's resistance? [take temperature coefficient of resistivity of copper, $a=6.8\times {10}^{-3}]$

A. $1.2\mathrm{m}\mathrm{\Omega }$  
B. $11.8\mathrm{m}\mathrm{\Omega }$
C. $2.3\mathrm{m}\mathrm{\Omega }$
D. $4.6\mathrm{m}\mathrm{\Omega }$

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Correct Answer: A