Why does competitive equilibrium pricing and output lead to

Why does competitive equilibrium pricing and output lead to a maximization of these surpluses?

Solution

Only perfect competition ensures that there is no deadweight loss in the market . If output is lesser or price is higher than competitive equilibrium then there is welfare loss in the economy . Only perfect competition ensures that consumer and producer surplus is maximized .

As for example in case of mnopoly some amount of consumer surplus is transferred to producer and deadweight loss occurs because of higher pricing and lower output .