The typical lifetime of a star like our Sun is 10 billion years. While a star like our Sun is able to generate energy in its core (through fusion) the thermal pressure balances the gravitational pressure from the Sun’s mass. However, once the star rules our of hydrogen, gravitational collapse can occur, and depending on the star’s mass it may become a white dwarf. A white dwarf is a dense stellar remnant with a typical radius of about 104 km.

Question

The typical lifetime of a star like our Sun is 10 billion years. While a star like our Sun is able to generate energy in its core (through fusion) the thermal pressure balances the gravitational pressure from the Sun’s mass. However, once the star rules our of hydrogen, gravitational collapse can occur, and depending on the star’s mass it may become a white dwarf. A white dwarf is a dense stellar remnant with a typical radius of about 104 km. 
a) If a star like our Sun (M = 2x1030 kg, R = 750,000 km, rotational period ~25 days) collapsed and became a white dwarf, what would its new rotational period be? Give your answer in minutes or seconds, not days. (Hint: there are no external torques on the system.) 
b) Does the kinetic energy of rotation increase, decrease, or stay the same? (Show your work for full credit.)