Help with Paypal Chained Payments App

Sorry to be a bother :slight_frown: I would love to know this without asking. I received coorespondence back from paypal x with some questions about my app. Here they are:

1) In your chained payment, who is the primary receiver and who is the secondary receiver? Also, who is paying PayPal fee? Is it primary receiver or secondary receiver or each receiver?
2) Do you have an Acceptable Use Policy publicly available? And where can we find it? If not, you can use PayPal's (https://cms.paypal.com/us/cgi-bin/marketingweb?cmd=_render-content&content_ID=ua/AcceptableUse_full&locale.x=en_US). However one must be posted due to there are activities that PayPal is restricted to its users. I will use Paypal's.
3) What is your fee or percentage structure of all sales on your site? 4%
4) Do you have a refund policy posted on your site? We strongly recommend that you have a refund policy posted on your site even if you don’t offer refund. Yes. It is posted on the "Gateway Settings Page Message"

I have answered all bu the first b/c I don't know what secondary receiver is and I don't know how to word that the shop owners pay the paypal fees. Can you please advise?