Afirecracker in a coconut blows the coconut into three pieces. two pieces of equal mass fly off south and west, perpendicular to each other, at 18 m/s. the third piece has twice the mass as the other two. what is the speed of the third piece? what is the direction of the third piece?

option number c is the right answer.

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