Consider a market in which consumption of the good being traded generates a positive externality. 

There are 100 identical consumers, each with a utility function given by 1/2√q+m+√G, where G denotes the total level of consumption in the market. 

The good is sold by competitive firms that produce with a constant marginal cost of 1 $/unit. 
now assume that the good is sold by a monopolist that produces using the same technology. 

In this case, what is the difference between the optimal level of total consumption and the level of total consumption in equilibrium