Internet service in the local market is supplied by Laura's Internet Service. The demand is QD = ...

If Laura can first-degree price discriminate, she will charge the highest price each consumer is willing-to-pay.  This implies she will continue selling units until the price of the last unit sold equals her marginal cost.            
   P = 65 - 0.01Q = MC = 6.67 + 0.0067Q
Therefore Q = 3,492.8   
Producer surplus is 
   PS = (0.5)(65 - 6.67)(3,492.81) = 101,867.80
Since the price of the last unit sold is equal to the marginal cost, Laura's output level is efficient.  However, since Laura is first-degree price discriminating, consumer surplus is zero.  Social welfare in this market structure is as high as possible given the efficient level of units are produced.