Final answer:
An owner must designate a mechanic's lien agent under the NC Mechanic's Lien statute if a new roof costing $42,000 is being placed on a vacation rental unit.
Step-by-step explanation:
Under the North Carolina Mechanic’s Lien statute, a property owner must designate a mechanic's lien agent (MLA) under specific circumstances related to construction and property improvement. The requirement to designate an MLA is triggered when the cost of the improvement to the property is $30,000 or more and it is not for improvements to a primary residence. Therefore, according to the choices provided, an owner must designate an MLA if a new roof is being placed on a vacation rental unit that costs $42,000. Improvements to public buildings or to a primary residence do not require the designation of an MLA, and the same applies to any improvements that cost less than $30,000.