The diagram below shows a production possibility frontier (PPF) for a regional economy that produces Green Energy (GGG, in GWh) and Industrial Steel (SSS, in kt).

Which point corresponds to a situation where the economy has underutilised or unemployed resources, meaning it can increase the production of Green Energy without incurring any opportunity cost (i.e., without reducing the production of Industrial Steel)?
Point Q
Point R
Point P
Point T