$2 \pi r = n \lambda \quad \because r=0.529 \frac{ n ^{2}}{ Z }$
$2 \pi \times 0.529 \frac{ n ^{2}}{ Z } A = n \lambda$
$\lambda=\frac{2 \times 3.14 \times 0.529 \times 2}{2} A$
$\lambda=3.33\,\mathop A\limits^o $