In the neoclassical model, only technology can bring a permanent increase in growth rate(for GDP per Capita) but in the EOC other factors such as increase in investment rate are identified as bringing about a higher rate of per capita incoem growth in economy.
I ‘get’ the answer since it makes sense but I am really confused what model to stick to while answering these questions? Any advice would be great.
BUMP
The central theme of neoclassical growth theory is that MPK = r; the marginal product of capital equals the cost of capital. This maximizes (net) output per dollar of capital.
An increase in the investment rate will change the MPK: it will reduce it. Thus, you need either an increase in technology or a decrease in the investment rate to return to MPK = r.
Take a look at the article I wrote on neoclassical growth theory; it may be useful: http://financialexamhelp123.com/neoclassical-growth-theory/.