9. The main conceptual difference between the Romer model and the Solow model is a. The production function in Romer exhibits decreasing marginal returns with respect to capital but Solow does not. b. The Romer model tries to explain how an economy can continue to grow year-after-year whereas the Solow model only has growth in the transition to steady state. c. The Solow model focusses on increasing returns to scale and the Romer model is focused on the steady state d. The Solow model is a model of growth in GDP per capita, but Romer is a model of growth in GDP per worker e. Both c. and d. are correct.