$7$ After a long period of cloudiness and a constant temperature of $20C,$ the sun breaks through the clouds in the

Poin?s: $5$

middle of the day and instantly heats up the surface of a very thick concrete pad to $40C,$ and the temperature of the surface stays constant at that temperature for an hour. What is the temperature of the concrete after the one hour, $10cm$ deep into the concrete? Assume a concrete density of $2500k\frac{g}{m^3},$ a thermal conductivity of $1\mathrm{.}5\frac{W}{m}K,$ and a specific heat of $1000\frac{J}{k}gK.$

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