\(V\) = 660 Hz
\(v\) = 330 m/s
\(\lambda = \frac vV = \frac{330}{660} = 0.5\)m
Thus the shortest distance b/w wall (node) and the point where the air particles have maximum amplitude of vibration (anti node)
\(d = \frac\lambda4\)
\(d = \frac{0.5}4\)
\(d = 0.125 m\)