How to make total price for split attachment, please?

I got the WINRar for splitting up large files into 10mb files. If there are several parts I divide the attachment price for the parts like for example 4 parts x 20 = 80 coins or 3 parts x 30 = 90 coin.  Is this necessary.  How to just have a total price for all the attachments?  

CraftyLouAnna

I agree with Puppy, makes it so much easier for the members too!  Having to pay for each part of the download is just more work.
Paying on the first file relieves the stress of perhaps missing a file or forgetting to pay.

pitussa

There is no need to split. Just put the total price on one of the parts.
Most people do that.

Puppy

Usually I put the total price to the first part.