Consider the Following Model of the IS Curve Without an International

Consider the following model of the IS curve without an international sector:
Consumption: $C _ { t } = \bar { a } _ { c } \bar { Y } _ { t }$
Investment: $I _ { t } = \bar { a } _ { t } \bar { Y } _ { t }$
Government expenditure: $G _ { t } = \bar { a } _ { g } \bar { Y } _ { t }$
With this formulation the IS curve is:

A) horizontal
B) less steeply sloped than the "standard" IS curve
C) vertical
D) more steeply sloped than the "standard" IS curve
E) Not enough information is given.