On January 1, 2020, Ophelia bought $2,000 worth of Kumquat Corp. Its value had risen to $2,800 on July 1, 2020, and she sold o $X of it. By the end of the year, the value of her Kumquat stock was $200, and she sold it all. If her time-weighted yield rate is equal to her dollar-weighted yield rate, what was $X, and what is that yield rate?