Bar Graphs

The bar graph below shows the test results of a class of students on five subjects.

1. Given that each student took tests on all five subjects, find the total number of students of the class.
2. Find the number of students who passed the test on Mathematics and English, respectively.
3. Find the number of students who failed the test on Physics and Chemistry, respectively.
4. Find the passing rate of Biology, expressed by the number of students who passed the test on Biology as a percentage of the total number of students of the class.
5. Without giving numerical calculations, state which subject has the lowest passing rate among the students of the class.