Answer
a) Aluminium
b) 83.68 Watts
Work Step by Step
We know:
$\Delta Q = m_wS_w\Delta T_w$
$\Delta Q = m_xS_x\Delta T_x$
Setting these equal to each other and simplifying gives:
$ S_x = \frac{\Delta T_w S_w m_w}{\Delta T_x m_x} \\ S_x = \frac{100\times10^{-3}\times 4184\times12}{100\times10^{-3}\times 56} = 900 \frac{J}{kg K }$
The material is $\fbox{Aluminum.}$
We now find the value of the heat flow rate:
$= \frac{\Delta Q}{\Delta t} = \frac{5020.8}{60}=\fbox{83.68 W}$