4. Bob, Kara, and Mark are partners in the BKM Partnership. Bob is a 40% partner and has a June 30 tax year-end. Kara owns a 40% interest in the partnership and has a September 30 tax year-end, and Mark owns the remaining 20% interest and has an October 31 tax year-end. The partnership does not have a natural business year. What is the required tax year-end for the partnership (if no Sec. 444 election is made)? a.June 30 b.September 30 c.October 31 d.December 31