Premise: Part of the reason for the difference in pieces per possible delivery may be due to the fact that five percent of possible residential deliveries are businesses, and it is thought, but not known, that a lesser percentage of possible deliveries on rural routes are businesses.

Hypothesis: It is thought, but not known, that a lesser percentage of possible deliveries on rural routes are businesses, and part of the reason for the difference in pieces per possible delivery, may be due to the fact that five percent of possible residential deliveries are businesses.
Relation: entailment