Final answer:
Bob's employer in Massachusetts must pay him at least $8.00 per hour, as it is the higher state minimum wage compared to the federal minimum wage of $7.25 per hour.
Step-by-step explanation:
The least hourly wage that Bob's employer may pay him in Massachusetts is $8.00 per hour. This is because when state and federal minimum wage laws differ, the higher wage prevails. In this case, the Massachusetts minimum wage is higher than the federal rate. Employers are required to pay employees the higher state minimum wage if it exceeds the federal minimum wage, hence the correct answer is $8.00 per hour.