Need help on number four & five. Thanks!

True or false: the revolution of the earth creates day and night as it rotates around the sun

Why is it important always to use horizontal bars in unit fractions when performing unit conversions?

The sun’s mass is 2.0×10^ 30 kg, its radius is 7.0×10 5 km, and it has a rotational period of approximately 28 days. if the sun should collapse into a white dwarf of radius 3.5×10 3 km, what would its period be if no mass were ejected and a sphere of uniform density can model the sun both before and after?