Physics - Modern Physics - Relativity - Time dilation and length contraction - The Twin Paradox Setup

Story scenario: 'Twins Alex and Beth are 20 years old. Beth boards a spaceship traveling at 0.9c to a star 9 light-years away, then returns. From Alex's perspective on Earth, the journey takes 20 years (10 years each way at 0.9c for 9 ly).' Question 1: 'When Beth returns, Alex is 40. How old is Beth