Answer: $6.00
Step-by-step explanation:
From the question, we can see that the productivity in the United States is (45/9) = 5 times higher than that of Mexico.
Therefore, the wages in Mexico should be 5 times lower than the wages paid to the workers in the United States. This will be:
= $30.00 / 5
= $6.00
Therefore, in order for the firm to reduce its wage cost per unit of output by moving to Mexico, the wages in Mexico must be below $6.00 per hour.