Sand Is Converted to Pure Silicon in a Three Step $\to$

Multiple Choice

Sand is converted to pure silicon in a three step process.The third step is
SiCl₄(g) + 2Mg(s) $\to$ 2MgCl₂(s) + Si(s) $\Delta$ H = -625.6 kJ
What is the enthalpy change when 25.0 mol of silicon tetrachloride is converted to elemental silicon?

A) -25.0 kJ
B) -7820 kJ
C) -1.56 $\times$ l0⁴ kJ
D) -3.13 $\times$ 10⁴ kJ
E) None of these choices is correct.