In New York, how do we pay restaurant staff for changing duties?

Q: “I’m in the restaurant industry in New York. My client has part-time workers that typically work four hours in the morning at one position. There are many times he needs additional help in the afternoon and asks them to stay. The afternoon job is at a lower pay rate. Is this considered a new job and therefore comes under the 3/4 hour minimum pay rule? What about the reduction in pay for the afternoon work? Sometimes they may work one or two hours in the afternoon position. Neither of these positions are server staff.” – Ken, NY