Data:

Cp $($specific heat capacity$)=3500$ J$/$kg

$=1000$ kg$/$m$3$

U $($overall heat$-$transfer coefficient$)=150$ W$/($m$2$K$)$

A $($interfacial area$)=6$ m$2$

Cooling water temperature $35$ oC

Ignore the thermal mass of the tank

How long will the tank take to cool?