"Amit" and "Bhanu" have respective completion times of 20 and 30 days for a task. They began working together on the project, but after a few days, "Amit" left and "Chintu," who can finish the entire task on her own in ten days, joined. Four days before the job was finished, "Chintu" left. Determine the amount of work completed by "Bhanu" if "Amit" and "Chintu" worked for a similar number of days.