On a hot summer day a concrete driveway may reach a temperature of 50◦C. Suppose that a stream of water is directed on the driveway so that the surface temperature is suddenly lowered to 10◦C. How...

On a hot summer day a concrete driveway may reach a temperature of 50◦C. Suppose
that a stream of water is directed on the driveway so that the surface temperature is
suddenly lowered to 10◦C. How long will it take to cool the concrete to 25◦C at a
depth of 5 cm from the surface?