An Atom of the element of Manosium has energy levels 1,2, and 3 with sucessively higher energy. When the atom makes the transition from level 3 to level 1, it emits a photon with wavelength of 500nm. When it makes the transition from level 2 to level 3, it absorbs a photon with a wavelength of 700 nm. What wavelength photon is emitted by the transition from level 2 to level 1?

so far,
E=hv
E(1to3)=E(1to2)+E(2to3).