A set of twins, Andrea and Courtney, are initially 10 years old. While Courtney remains on Earth, Andrea rides on a spaceship that travels away from Earth at a speed of 0.60c for 10 years (as measured by Courtney). At the end of the trip, Courtney is 20 years old. How old is Andrea

How does the principle of federalism affect the u.s. government? a. it guarantees that the united states will always be a representative democracy b. it ensures that the state governments have greater authority that the federal government c. it creates both separate and overlapping powers for the federal and state governments d.it divides the federal and state governments into three branches