What is the change in the orbit radius when the electron in the hydrogen atom (Bohr model) undergoes the first Paschen transition ?

rn =0.529 × n2Z Aor4−r3=0.529  × 161 −0.529 × 91Ao         =0.529(16-9)Ao=  0.529  × 10−10  16−9m=7  ×  0.529  × 10−10=  3.7  × 10−10  m