At a discount brokerage, a stock purchase or sale worth less than $10,000 incurs a brokerage fee of 1% of the value of the transaction. A transaction worth more than $10,000 incurs a fee of $100 plus 0.5% of the amount exceeding $10,000. Note that for a fraction of a cent, the brokerage always charges the customer a full penny. You wish to buy 100 shares of a stock whose price D in dollars has PMF
What is the PMF of C, the cost of buying the stock (including the brokerage fee)