line 27 student needs to be titlecase.
there's more:
s1, s2, and s3 are classes of Student, they are not strings.
Therefore you must treat then as such.
You are too liberal with the use of name student and Student (which are two different objects)
there's more:
s1, s2, and s3 are classes of Student, they are not strings.
Therefore you must treat then as such.
You are too liberal with the use of name student and Student (which are two different objects)