Do problem #$18-18,$ pg $381$

$$ A solid concrete wall is $80$ ft high, $100$ ft wide, and $6$ in$.$ thick.$$ The$$ surface temperatures on the sides of the concrete are $30$ and$$

$100$ oF$.$ What time is required for $400,000$ Btu of heat to be transferred?

Group of answer choices

$0\mathrm{.}125$ hr

$2\mathrm{.}23$ hr

$1\mathrm{.}36$ hr

$0\mathrm{.}765$ hr