Suppose a wall divides a playground, and twenty balls lie on the ground on the east side, while forty balls lie on the west side. if a child on the east side of the wall always tosses a ball over the wall at the same time a child on the west side tosses a ball over the wall, then:

i think the answer is a, hope this : )

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