A dim sum restaurant can deliver their food by cart or by hand. Servers can deliver by cart and have 70 customer interactions and will have to refill food five times an hour. They can also deliver more food by hand, due to the increased mobility, and have 85 customer interactions while refilling food twenty times an hour. However, the customers get more options when delivering by cart, therefore at least 70% of delivery shifts must be by cart. There must be at least 3 servers delivering by hand for their direct customer service. If the restaurant wants to have 4000 customer interactions per hour, how many of each form of delivery should the dim sum restaurant schedule to minimize the total number of refills per hour?