System of Linear Equations

Q. The system of equations
$x+3y+2z=6x+ay+2z=7x+3y+2z=b$
has

1. a unique solution, if $a=2$ and $b\ne 6$
2. infinitely many solutions, if $a=4$ and $b=6$
3. no solution, if $a=5$ and $b=7$
4. no solution, if $a=3$ and $b=5$

Q. If the system of equations $2x+3y-z=0,x+ky-2z=0$ and $2x-y+z=0$ has a non-trivial solution $(x,y,z)$, then $\frac{x}{y}+\frac{y}{z}+\frac{z}{x}+k$ is equal to :

1. $\frac{3}{4}$
2. $-4$
3. $-\frac{1}{4}$
4. $\frac{1}{2}$