Man with wives..

Just now,when i was checking my emails, i came across this title 'Man with wives' and it was sent by Lee Ping a few days ago, so i click this was what i saw..
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Only skilled people can open this file....... Once you succeed to open this file, you will find names of smart people who have managed to open this...... Now it is your turn!
How to open attached file?

A man was traveling to Kasoa
At the bus stop, he met a man with 7 wifes
Each wife has 12 sons and 12 daughters
Each daughter of the man's wifes had 4 sons and 7 daughters
Each son of the man's wifes had 7 sons and 4 daughters
Each grand daughter had 4 friends
How many people got to kasoa?

The number of people who got to kasoa is the password to open attached file. Once opened, add Your name and pass it on to challenge others…
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woo..nice IQ question huh! So I took my calculator and start calculate..and at last..my answer was 5720.I try to open the file by using this numbers but..boohoohoo..it said my answer was wrong!so i think back and remember that i forgot to add the man who met another man with 7 wives,so add one and it became 5721. Thinking that this should be the correct answer, i went to try again and AGAIN..it said my answer was wrong!!Argh...then i took a paper and draw out the 'family tree' and count again and my answer was the same as the previous one : 5721... Hum..Did i really count wrong or there's something wrong with that file arr?

Anyone know the answer??Lee Ping sure know the answer, fast fast tell me lerr, i want to open the file and see what is inside! and most importantly, i wana add my name inside leh!!hahaha...