Dear Ai Lin,
I received your letter yesterday .Thank you for
Iam sorry that i shall not be attend your birthday party . It is also my father's birthday and we are having a party for him. As such,I shall be expected to be here for the happy occasion .
Please accept my humble apologies and I hope that you and your friendswill have a good time.
I also take this opportunity to wish you 'A Very Happy Bitrhday'.
Your loving friend,