A solid metal rod $50$ mm diameter, $65$ mm long, initially at $650C,$ is quenched during heat treatment in a fluid at $90C.$ The surface heat transfer coefficient is $850\frac{W}{m^2}K.$ Plot the variation of temperature at centre point with the time after immersion $5$ secs to $3$ min $.[10]$

$=17\mathrm{.}7{10}^{-6}\frac{m^2}{s},=7854k\frac{g}{m^3}$;$C_p=434\frac{J}{k}gK$;$k=60\mathrm{.}5\frac{W}{m}C$