If the straight lines $x=1+s, y=-3-\lambda s, z=1+\lambda s$ and $x=\frac{t}{2}, y=1+t, z=2-t$ with parameters $s$ and $t$ respectively, are coplanar, then $\lambda$ is equal to:

3 -2 -1 5

-2

The correct answer is Option (2) → -2