Let the system of equations:
\( 2x + 3y + 5z = 9 \),
\( 7x + 3y - 2z = 8 \),
\( 12x + 3y - (4 + \lambda)z = 16 - \mu \),
have infinitely many solutions. Then the radius of the circle centred at \( (\lambda, \mu) \) and touching the line \( 4x = 3y \) is: