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A hot body , obeying Newton's law of cooling is cooling down from its peak value $\;80^{0}C\;$to an ambient temperature of $\;30^{0}C\;$ . It takes 5 minutes in cooling down from $\;80^{0}C\;$ to $\;40^{0}C\;$. How much time will it take to cool down from $\;62^{0}C\;$ to $\;32^{0}C\;$ ? (Given ln 2=0.693 ; ln 5=1.609)

$(a)\;3.75\;minutes \qquad(b)\;8.6\;minutes\qquad(c)\;9.6\;minutes\qquad(d)\;6.5\;minutes$

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