Frequently, someone forgets to put the drinks into the ice chest before the picnic starts. 

suppose that you have a can of soda that is at the ambient temperature of 32°C and that you are interested in cooling a can of soda (13 cm long and 6 cm in diameter) as rapidly as possible. You decide to put the can into the water/ice slush in the cooler and shake it to induce fluid currents inside the can that will (you think) maintain a spatially uniform temperature in the soda can as it cools (Modeling the soda as pure water with ρ=1,000 kg/m³ and c=4,178 J/kg-K). 

a) Supposing the heat transfer coefficient between the slush and the can is 40 W/m² -K, how long will it take to cool the drink to 4°C? 

b) Please show that the thermal resistance of the aluminum in the can be neglected, by computing the Biot number (pure aluminum with k=237 W/m-K and thickness of 1 mm). 

c) Please estimate how long does it take the soda to warm back up to 25°C if it is left on the picnic table? You may assume natural convection in the soda maintains a spatially uniform temperature distribution in the soda. (h(air)=10 W/m² K).