A company has established that the relationship between the sales price for one of its product and the quantity sold per month is approximately p = 75 - 0.1D units (D is the demand or quantity sold per month and p is the price in dollars). The fixed cost is $1,000 per month and the variable cost is $30 per unit produced. (a) What is the maximum profit per month related to this product? (b) What is the range of profitable demand during a month?