On National Day, Jack, a middle school student, went to Harbin Wanda Amusement Park with his three classmates. According to the price list, they saved________ of the cost on usual days.
Adult (age 60 and above) | Adult (age under 60) | Child (age 6-17) | Child (age under 6) |
Free | ¥200 | ¥150 | Free |
October 1st: 20% off |