Final answer:
Mateo's holding period for the machinery he obtained in the exchange began on June 4, 2015.
Step-by-step explanation:
Mateo's holding period for the machinery he obtained in the exchange began on June 4, 2015.
The holding period for an asset received in a nontaxable exchange starts on the same day as the holding period for the asset that was traded. In this case, Mateo traded the machinery on June 4, 2015, so his holding period for the new machinery begins on the same day.