<s>[INST] Krugman (1961) describes the following model:
$$
X = A I + B Y
$$
$$
Y = C + D X
$$
$$
M = E + F Y + G R
$$
$$
Y = L\cdot R
$$
Substituting equation (2) in (1), we obtain:
$$
X = A I + B(C + D X)
$$
$$
\Rightarrow \ \ \ X(1-BD) = A I + BC
$$
$$
\Rightarrow \ \ \ X = \frac{A I + B C}{1 - B D}
$$
Substituting equation (4) into (3), we get:
$$
M = E + F\cdot L\cdot R + G R
$$
$$
\Rightarrow \ \ \ M = (E + F\cdot L\cdot R + G R)
$$
$$
\Rightarrow \ \ \ M = (E + (F\cdot L + G) R)
$$
These are the reduced form equations. If there is  a unit increase in G, what happens with R?[/INST]