What is the photon energy corresponding to the wavelength

Question

Exposure to a sufficient quantity of ultraviolet will redden the skin, producing erythema ?a sunburn. The amount of exposure necessary to produce this reddening depends on the wavelength. For a 1.0 cm² patch of skin, 3.7 mJ of ultraviolet light at a wavelength of 254 nm will produce reddening; at 300 nm wavelength, 13 mJ are required.

Part A

What is the photon energy corresponding to the wavelength of 254 nm?

Part B

What is the photon energy corresponding to the wavelength of 300 nm?

Part C

How many total photons with the wavelength of 254 nm produce this reddening of the 1.0 cm² of the skin?

Part D

How many total photons with the wavelength of 300 nm produce this reddening of the 1.0 cm² of the skin?