Section 704(e)(1) recognizes a partner if he owns a capital interest in a partnership in which capital is a material income-producing factor. Consider whether the statutory requirement is satisfied in the following situations:

(a) Father is a lawyer who makes Son (a contractor) and Daughter (a student) partners in his sole practitioner law firm.

(b) Father is a lawyer who makes Daughter (a law-school graduate who has recently passed the bar) a partner in his sole practitioner law firm.

(c) Father owns a building subject to a 10-year lease and he transfers the building along with the lease to a partnership with Son and Daughter.

(d) Father transfers just the lease in part (c), above, to the partnership.

(e) Same as part (c), above, except Father retains the right in any year to allocate the income to any of the partners and to give the building to Mother.