An object at temperature `70^(@)C` is placed in a surrounding medium of temperature `30^(@)C` . Its temperature decreases by `10^(@)C` in first 5 min. Find the time interval from starting in which its temperature reduces to `40^(@)C`. Assume Newton's law to be valid.
`t = 0 " "T = 70^(@)C" "T_("env") = 30^(@)C`
`t = 5 " "T = 60^(@)C" "T_("env") = 30^(@)C`
time = t T = `40^(@)" " T_("env") = 30^(@)C`

Explanation

To solve the problem using Newton's law of cooling, we will follow these steps:

### Step 1: Understand Newton's Law of Cooling
Newton's law of cooling states that the rate of change of temperature of an object is proportional to the difference between its temperature and the ambient temperature. Mathematically, it can be expressed as:
\[ -\frac{dT}{dt} = k(T - T_{\text{env}}) \]
where:
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