5.02: (a) If a star more massive than the Sun is characterized by M = 2 x 1035 g and L = 4 x 1040 erg/s, how long can it shine at that luminosity if it is 100% hydrogen and converts all H to He?
(b) Do a similar calculation for a red dwarf star of mass 1033
g and luminosity 4 x 1032 erg/s.