*, brainliest to first correct answer*

a roller derby exhibition recently came to town. they packed the gym for two
consecutive weekend nights at south's field house. on saturday evening, the
68-kg anna mosity was moving at 17 m/s when she collided with 76-kg sandra
day o'klobber who was moving forward at 12 m/s and directly in anna's path.
anna jumped onto sandra's back and the two continued moving together at
the same speed. determine their speed immediately after the collision.

show your work, so i can follow through

People with normal vision cannot focus their eyes underwater if they aren't wearing a face mask or goggles and there is water in contact with their eyes. in a simplified model of the human eye, the aqueous and vitreous humors and the lens all have a refractive index of 1.40, and all the refraction occurs at the cornea, whose vertex is 2.60 cm from the retina. with the simplified model of the eye, what corrective lens (specified by focal length as measured in air) would be needed to enable a person underwater to focus an infinitely distant object? (be careful-the focal length of a lens underwater is not the same as in air! assume that the corrective lens has a refractive index of 1.62 and that the lens is used in eyeglasses, not goggles, so there is water on both sides of the lens. assume that the eyeglasses are 2.05cm in front of the eye.)