Let the plane passing through the point \( (-1,0,-2) \) and perpendicular to each of the planes \( 2x+y-z=2 \) and \( x-y-z=3 \) be \( ax+by+cz+8=0 \). Then the value of \( a+b+c \) is equal to:
\( 5 \)
\( 8 \)
\( 3 \)
\( 4 \)