Part b, please answer with exact values

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?

What does si stand for, when referring to a system of measurement

Abeam of electrons moves at right angles to a magnetic field of 4.5 × 10-2 tesla. if the electrons have a velocity of 6.5 × 106 meters/second, what is the force acting on the electrons? the value of q = -1.6 × 10-19 coulombs.