Option 1 -> Unskilled workforce affects productivity but doesn't justify fixed prices.
Option 2 -> Scarcity exists in all economies and typically leads to price adjustments, not fixed prices.
Option 3 -> Excess use of resources creates capacity constraints leading to price increases, not fixed prices.
Option 4 -> When resources are unused (idle labor, excess capacity), output can expand without price pressures.
Hence, An economy with unused resources -> In Keynesian economics, the fixed price assumption holds when there are unemployed resources and spare capacity in the economy. When firms have idle resources, they can increase production in response to higher demand without facing capacity constraints or cost pressures. This means output can expand without causing prices to rise, justifying the assumption of fixed price levels in the short run. This scenario typically occurs during recessions or when the economy operates below full employment. -> correct