Answer:
According to the sticky-wage theory, the economy is in a recession because the price level has declined so that real wages are too high, thus labor demand is too low.
According to the sticky-price theory, the economy is in a recession because not all prices adjust quickly.
According to the misperceptions theory, the economy is in a recession when the price level is below what is expected.
Step-by-step explanation:
The above mentioned are the three theories of the upward slope of the short-run aggregate-supply curve.