When a certain metal was irradiated with light of frequency $$3.2 \times10^{16}\ \mathrm{Hz}$$, the photoelectrons emitted had twice the kinetic energy as those emitted when the same metal was irradiated with light of frequency $$2.0 \times10^{16}\ \mathrm{Hz}$$. The threshold frequency $$v_0$$ of the metal is

A

$$2.4 \times10^{16}\ \mathrm{Hz}$$

B

$$8.0 \times10^{16}\ \mathrm{Hz}$$

C

$$8.0 \times10^{15}\ \mathrm{Hz}$$

D

$$7.2 \times10^{16}\ \mathrm{Hz}$$