A cup of coffee cools from \(90^{\circ}\text{C}\) \(80^{\circ}\text{C}\) in \(t\) minutes, when the room temperature is \(20^{\circ}\text{C}.\) The time taken by a similar cup of coffee to cool from \(80^{\circ}\text{C}\) \(60^{\circ}\text{C}\) at room temperature same at \(20^{\circ}\text{C}\) is:
| 1. | \(\dfrac{10}{13}t\) | 2. | \(\dfrac{5}{13}t\) |
| 3. | \(\dfrac{13}{10}t\) | 4. | \(\dfrac{13}{5}t\) |
An object kept in a large room having an air temperature of \(25^\circ \text{C}\) takes \(12 ~\text{min}\) to cool from \(80^\circ \text{C}\) to \(70^\circ \text{C}.\) The time taken to cool for the same object from \(70^\circ \text{C}\) to \(60^\circ \text{C}\) would be nearly:
| 1. | \(10 ~\text{min}\) | 2. | \(12 ~\text{min}\) |
| 3. | \(20 ~\text{min}\) | 4. | \(15 ~\text{min}\) |