Pursuant to a contract, a landscaper performed $30,000 of landscape work for a homeowner. by coincidence, the homeowner and the landscaper were involved in an automobile accident that was unrelated to the landscape work. the homeowner was injured in the accident and sued the landscaper in federal district court for negligence, seeking $100,000 in damages. the homeowner and the landscaper are citizens of different states. may the landscaper assert and maintain a counterclaim against the homeowner for breach of contract, seeking the $30,000 due under the landscape contract?