a b c d

c

$\Delta E = 13.6 z^2 (\frac{1}{n^2} - \frac{1}{m^2})$ $\Delta E = 13.6 3^2 (\frac{1}{1^2} - \frac{1}{3^2}) = -13.6 \times 9 (1 - \frac{1}{9}) = 13.6 \times 8 = 122.4 J$