A calorimeter of negligible heat capacity contains 100cc of water at `40^(@)C` . The water cools to `35^(@)C` in 5minutes. The water is now replaced by k-oil of equal volume at `40^(@)C` . Find the time taken for the temperature to become `35^(@)C` under similar conditions. Specific heat cpacities of water and K-oil are `4200Jkg^(-1)K^(-1)` and `2100Jkg^(-1)K^(-1)` respectively. Density of K-oil `=800kgm^(-3)` .