Final answer:
The tax year-end for Partnership TNT would likely be June 30th to align with TNT Techtron Inc, subject to IRS approval or elections made by the partnership.
Step-by-step explanation:
The question pertains to the determination of a tax year-end for a partnership based on the ownership interests of its partners. Since Melissa and Melinda each own a 20% interest in Partnership TNT Techtron Inc, which in turn owns a 60% interest in Partnership TNT, the majority interest method for determining the tax year-end would typically be applied. However, the IRS also allows partnerships to elect a different tax year-end under certain conditions. If none of these conditions are met and an election is not made, the IRS default rule would likely set the tax year-end for Partnership TNT to be the same as TNT Techtronic's year-end, which is June 30th.