If 2n=10 how many sister chromatids are present at prophase of mitosis

2n = 10
/2       /2
n = 5 

5 sister chromatids. 

No because the eaeht is on a 23.5 degree axis tilt and so when it is winter the northern hemisphere is pointing away from the sun and the soutubern hemisphere is pointing toward the sun

The anwser is the universe