Solve the System $\begin{array} { l } 4 x - 7 y - z = - 17 \\x + 3 y - 5 z = - 9 \\3 x + y + z = 21\end{array}$

Multiple Choice

Solve the system.
$\begin{array} { l } 4 x - 7 y - z = - 17 \\x + 3 y - 5 z = - 9 \\3 x + y + z = 21\end{array}$

A) $\varnothing$
B) $\{ ( 4,5,4 ) \}$
C) $\{ ( - 4,4,8 ) \}$
D) $\{ ( 4,4,5 ) \}$