You are the lab assistant, and the specimen is the economy. A shock — a stock crash, an oil embargo, a stimulus bill — opens a gap between current output (Y) and potential output (Yf). Walk the chain that closes the gap, then close it yourself before the clock runs out.

The classical model: a gap moves the labor market, the labor market moves wages, wages move per-unit costs, and costs shift SRAS until equilibrium returns to Yf.