An aluminium container of mass 100 g contains 200 g of ice at $-\text{20°C}$ . Heat is added to the system at a rate of 100 cal/s. The temperature of the system after 4 minutes is (Specific heat capacity of ice $=\text{0}\text{.5}\text{cal/g}-\text{°C}$ , specific heat capacity of aluminium $=\text{0}\text{.2}\text{cal/g}-\text{°C}$ , specific heat capacity of water $=\text{1}\text{cal/g°C}$ and latent heat of fusion of ice $=\text{80}\text{cal/g}$ .)