Able, Baker, and Carr formed the ABC Partnership in 2001. In 2002 Able gave her three sons, Duncan, Eldon, and Frederick, a gift of her 41 percent interest in the partnership to provide money to pay for their college expenses. The sons reported income from the partnership on their individual tax returns, and the partnership reported the payment to them on its information return. The sons were listed as partners on unaudited balance sheets in 2003, and the 2004 income statement listed them as partners. The sons never requested information about the management of the firm, never attended any meetings or voted, and never attempted to withdraw the firm's money or even speak with the other partners about the firm. Two of the sons didn't know where the firm was located, but they all once received "management fees" totaling $3,000, without any showing of what the "fees" were for. In 2005, the partnership incurred liability for pension-fund contributions to an employee, and a trustee for the fund asserted that Able's sons were personally liable under federal law for the money owing because they were partners. The sons moved for summary judgment denying liability. How should the court rule?