Equilibrium requires balancing supply and demand, but change unspecified

Steps:

• Set Q_s = Q_d for initial equilibrium: P - 30 = 20P + 30 yields inconsistent negative price, suggesting equation error (likely Q_d = 50 - P).
• Assuming corrected Q_d = 50 - P, solve P - 30 = 50 - P → 2P = 80 → P = 40.
• No change described (e.g., shift in curve or tax), so impact on price cannot be calculated.
• Not enough information to determine price effect.

Why C is correct:

• Cannot confirm; lacks details on change per supply-demand equilibrium law.

Why the others are wrong:

• A: No basis for $6 fall without specified demand increase or supply decrease.
• B: No basis for $2 fall.
• D: No basis for $6 rise.

Not enough information.

Final answer: Not enough information.