A teacher has given the following assignment to the children 'Your friend was absent from the class and missed the lesson on Area and Perimeter. Write a letter to him explaining the difference between the two. You can use diagrams also'.

The purpose of giving such kind of task in mathematics is

i. to know student's understanding of the concept taught

ii. to help the absentee student complete his missed work

iii. to teach the student how to write a letter

iv. to enhance student's mathematical communication