Economic question people answer?

Question

If an economy consumes 75 percent of any increase in income, then an increase in autonomous investment of $1 billion could result in an increase in Real GDP of as much as?

Answer 1

ΔY/ΔI=1/(1-MPC)

MPC=0.75

ΔI=+1

ΔY/1=1/(1-0.75)=1/0.25

ΔY=1/0.25=100/25= +4 = +$4 billion