Dear Hung,
Thanks a lot for your letter. It’s great to hear that you are going for a picnic to Cuc Phuong National Park next weekend. But I’m really sorry I can’t join you because I'm having a test in Maths on Monday, so I have to prepare for it. Let’s make it another time perhaps.
Thanks for thinking of me, and give my best regards to your parents. Have a great time on your picnic.
Your friend,
Lan sexy