A store selling art supplies finds that they can sell x sketch pads each week at a price of p dollars each, according to the formula x = 1000 − 400 p. What price should they charge (in interval notation and rounded to the nearest cent) if they want to sell a . At least 625 pads each week? b . More than 300 pads each week?

c . Less than 200 pads each week? d . At most 475 pads each week?