If the system of equations \( x + 5y + 6z = 4 \), \( 2x + 3y + 4z = 7 \), \( x + 6y + az = b \) has infinitely many solutions, then the point \( (a,b) \) lies on the line:
\( y - x = 3 \)
\( x - y = 3 \)
\( x + y = 11 \)
\( x + y = 12 \)