In the recent case, the stock fell and formed a point at this position.
A a= 17.7 The price is 17.7, then it bounces back to the high point B, and after b=2 1.2, it turns to point C, and the price is 19. Then, multiply 2 1.2 by 19 and divide it by 17.7 to get the final price of rising high point D.