The current theory of the structure of the Earth, called plate tectonics, tells us that the continents are in constant motion. Assume that the North American continent can be represented by a slab of rock 4000 km on a side and 27 km deep and that the rock has an average mass density of 2790 kg/m3. The continent is moving at the rate of about 3.8 cm/year. What is the mass of the continent?
Answer in units of kg.

i don't know that i agree with that but what's the question ?

answer a fan shaped mass of sediment deposited at the base of a mountain front do to an abrupt change in stream gradient;

you'd use the equation that establishes a relationship between  energy  and  wavelength, which looks like this

e=h⋅cλ, where

λ  - the wavelength of the photon; c  - the speed of light, usually given as  3⋅108m/s; h  -  planck's constant, equal to  6.626⋅10−34j s

plug the value you were given for the energy of the photon in the above equation to get the wavelength

e=h⋅cλ⇒λ=h⋅ce

λ=6.626⋅10−34js⋅3⋅108ms−1.257⋅10−24j=1.581⋅10−1m