A heat lamp produces 21.0 watts of power at a wavelength of 6.3 μm. How many photons are emitted per second?
a) 3.33 x 10¹⁹ photons/s
b) 2.10 x 10²² photons/s
c) 1.26 x 10²¹ photons/s
d) 7.14 x 10¹⁷ photons/s