I assume you are studying Maths. Where are you studying? Your profile says you are a native English speaker, from Singapore and your current location is Singapore. If you are studying maths in Singapore, I cannot understand why you are writing to a Singaporean Head of Department in English and, and if English is your native language, why do you not write like a native English speaker?
This is your second post. If your member profile is not accurate and you have not told the truth on it, I wouldn't bother writing a third post.