The cost , in dollars, of running a machine for hours is modeled by the function for . Which of the following is the best interpretation of the vertex of the graph of in the -plane?
The minimum cost is $5 when the machine runs for 10 hours.
The machine runs for a minimum of 5 hours.
The minimum cost is $10 when the machine runs for 5 hours.
The machine runs for 10 hours at a minimum cost of $5.
