A manufacturer of tennis rackets finds that the total cost C(x) (in dollars) of manufacturing x rackets/day is given by:

C(x) = 400 + 4x + 0.0001x²

Each racket can be sold at a price of p dollars, where p is related to x by the demand equation p=10-0.0004x. If all rackets that are manufactured can be sold, find the daily level of production that will yield a maximum profit for the manufacturer.