In the Long Run, If the Marginal Product of Capital $I _ { t } = \bar { a } _ { i }$

In the long run, if the marginal product of capital equals the real interest rate, investment is given by:

A) $I _ { t } = \bar { a } _ { i }$
B) $I _ { t } = \bar { a } _ { i } Y _ { t }$
C) $I _ { t } = \bar { a } _ { i } \bar { Y } _ { t }$
D) $l _ { t } = \tilde { Y } _ { t } / \bar { a } _ { i }$
E) $I _ { t } = \left[ \bar { a } _ { i } - \bar { b } \left( R _ { t } - \bar { r } \right) \right] \tilde { Y } _ { t }$