The death list in a school bus accident that happened on Wednesday morning in the northwest province of Gansu has risen to 20 following the death of one child later Wednesday. It's known that the accident happened around 9:40 a.m. in Yulinzi town of Zhengning county, according to a report from the police. The report said five people including four children and their bus driver died just at the moment that the accident happened. While 15 others, their teacher included, were sure to be dead by the afternoon. It's reported that another 44 children were injured in the accident and have been sent to hospital. Twelve of the injured are in badly hurt. The truck which caused the accident was carrying coal. Another reason for the accident was the bus itself. The police has blamed  _ for the accident, saying that the bus -- a van with nine seats -- was carrying 64 people. How many more people did the bus carry than it could be carried in?
9 15 64 55