Read this and answer the question. If the question is unanswerable, say "unanswerable".

In terms of school casualties, thousands of school children died due to shoddy construction. In Mianyang City, seven schools collapsed, burying at least 1,700 people. At least 7,000 school buildings throughout the province collapsed. Another 700 students were buried in a school in Hanwang. At least 600 students and staff died at Juyuan Elementary School. Up to 1,300 children and teachers died at Beichuan Middle School.

How many schools collapsed in Mianyang City
seven