In the 29th century, the Earth has become uninhabitable and humans have left it, living in starships that orbit around the planet. They have become unable to work due to their laziness, microgravity, and prolonged time in front of computers. Everything is hence produced by machines and robots: the production function is Y = zK . Referring to this economy, mark the correct answers.

a. Sustained growth in living standards can last forever without need of technological advances.

b. Sustained growth is only possible with technological advances.

c. An increase in the saving rate can only increase the growth rate temporarily

d. An increase in the saving rate permanently raises the growth rate of the economy.