Light of frequency 8.4x10¹⁴ Hz is incident on a metal surface. The stopping potential for this metal at this frequency is 2.8 V. What is the cutoff frequency of this metal?
O 3.2 × 10¹⁴ Hz
O 1.6 × 10¹⁴ Hz
O 8.4 × 10¹⁴ Hz
O 7.3 × 10¹⁴ Hz
O 4.5 × 10¹⁴ Hz