The schwarzschild radius of a black hole is r_s = 2 g m_bh / c^2.
derive the schwarzschild radius of the universe during the planck time, r_s, p.

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it

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