The minimum energy that must be possessed by photons in order to produce the photoelectric effect with platinum metal is:
[Given: The threshold frequency of platinum is $1.3 \times 10^{15} \mathrm{~s}^{-1}$ and $\mathrm{h}=6.6 \times 10^{-34} \mathrm{~J} \mathrm{~s}$.]