Given that \[T=\frac{2\,\pi \,l}{\sqrt{{{l}^{2}}+{{g}^{2}}}},\] find the value of T if \[\pi =3.142,\,\,\,l=7.89\] and \[g=9.81\], (Give your answer correct to 3 significant figures.)

• A.  \[3.94\]        
• B.  \[394\]     
• C.  \[39.4\]   
• D.      \[4.39\]