A trader has a margin account with total cash deposit of $20, 000. He bought 400 shares of a stock at the price of $100. If the minimum margin maintanance is 25%, what price of the stock today would lead to a margin call on his account? If withdraw is allowed at the margin ratio is above 50% after the withdraw, What price of the stock today would allow him to withdraw $2, 000 cash from the margin account?