i'm not too good at this topic, but i think question 1 is right
2: t0 is the time of the observer, tv(1.25)*sqrt(1-0.8^2) = t0 = 0.75years
remember when given a speed as a % of c u can sub it in as like sqrt(1-[(0.8c)^2]/[c^2]) and the c's will cancel, easier and less chance of mistake
even...