A gun fires a lead bullet of temperature 300k into a wooden block.the bullet having melting temperature 600k penetrates into block and melts down . If the total heat 625j then mass of bullet _____grams [L=2.5x10^4 j/kg],[S=125 j/kg k

$\begin{array}{rl}& 625=\mathrm{ms}\mathrm{\Delta }\mathrm{T}+\mathrm{mL}\\ & 625=\mathrm{m}[125\times 300+2.5\times {10}^4]\\ & 625=\mathrm{m}[37500+25000]\\ & 625=\mathrm{m}[62500]\\ & \mathrm{m}=\frac{1}{100}\mathrm{kg}\\ & \mathrm{M}=10\text{grams}\end{array}$