$[9-10]$ A $0\mathrm{.}6$ em diemeter milia steel cylinaricai rod et $100C$ is suddenty immersed in a liquid et $20C$ with convection neat transfer coemcient $h=400\frac{W}{m^2}.$ K$.$ The mild steel rod nas $k=43\frac{W}{m}.$ K$,c_p=473\frac{J}{k}g.K$ and $=7801k\frac{o}{m^3}.$ Answer probiems $(16-17)$ :

The time required for the rod to cool to $80C$ is:

A$.45$

B$.2$ s

C$.15$

D$.35$

E$.$ None of the above

If the length of the rod is $50$ cm $,$ the heat transfer rate from the rod to the liquid when the rod temperature cooled to $80C$ is:

A$.0\mathrm{.}68$ W

B$.75\mathrm{.}4$ W

C$.226\mathrm{.}2$ W

D$.301\mathrm{.}6$ W

E$.$ None of the above