You are the lab assistant. The specimen on the slab is the economy. When a shock hits — a stock crash, an oil embargo, a stimulus bill — the specimen falls out of long-run equilibrium and a gap opens between current output and potential output (Y vs. Yf).

The classical model says the economy heals itself: a gap moves the labor market, the labor market moves wages, wages move per-unit costs, and costs move SRAS until equilibrium returns to Yf. Your job is to walk that chain, then operate it under pressure.