Is there anyway to get a tutorial on how to build the following:

Design an Essay class that extends the GradedActivity. The Essay class should determine the grade a student receives for an essay. the student's essay score can be up to 100 and is determined in the following manner:
Grammar: 30 points
Spelling: 20 points
Correct Length: 20 points
Content: 30 points

Demonstrate the class in a simple program.