Final answer:
The slope of the long-run aggregate supply (LRAS) curve is vertical, representing no change in output level with shifts in aggregate demand, and thus leading to a vertical Phillips Curve showing no long-run tradeoff between inflation and unemployment.
Step-by-step explanation:
The slope of the long-run aggregate supply (LRAS) is indeed vertical. According to the neoclassical perspective on economics, in the long run, the quantity of output is determined by the supply of factors of production and not by the price level.
This results in a vertical LRAS at the level of potential GDP, where all unemployment is at the natural rate of unemployment. Consequently, shifts in aggregate demand do not change the level of output but do lead to price level changes.
Regarding the related concept of the Phillips Curve, which shows the relationship between inflation and unemployment, a vertical long-run Phillips Curve indicates that there is no long-run tradeoff between inflation and unemployment. If the natural rate of unemployment is, for instance, 5%, the curve will be vertical at that unemployment rate, showing that whatever the inflation rate, unemployment does not change from its natural rate.