Answer
$6.377\times 10^{-34}J.s$
Work Step by Step
We can find Planck's constant as follows:
$h=\frac{K_2-K_1}{f_2-f_1}$
We plug in the known values to obtain:
$h=\frac{(2.480\times 10^{19}J)-(1.260\times 10^{-19}J)}{(738.8\times 10^{12}Hz)-(547.5\times 10^{12}Hz)}$
$h=6.377\times 10^{-34}J.s$
