Find all vectors $u$ that satisfy the equation $($:$1,1,1$:$)u=($:$-4,1,3$:$).$

Select the correct choice below and, if necessary, fill in the answer boxes to complete your choice.

A$.$ The unique solution is $u=$

B$.$ There are infinitely many solutions of the form $u=1),$ where $z$ is any real number.

C$.$ There is no solution.