Answer:
If a firm decreases its sustainable growth rate (g), the price of their stock will probably decrease. I will use the following example:
P₀ = Div₁ / (Re - g)
P₀ = $2 / (12% - 5%) = $28.57
if the growth rate g decreases to 2%, and the rest remains unchanged, then
P₀ = $2 / (12% - 2%) = $20