Two planets of equal mass moving in opposite directions collide and coalesce at a distance d from the Sun. At the time of their elastic collision one planet is at perihelion and the other at aphelion, and both orbits have the same eccentricity e. Find the semi-major axis of the orbit of the joint mass.

the answer is 3.1 his answer is wrong mines is right

answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.

i think the answer is tomato juice? not entirely sure though