Norma Jean wants to unionize her fellow workers at Metro West Ambulance Company. She gets a majority of the workers who will be represented by the union to sign authorization cards, but despite this result, Metro West refuses to recognize the union. To hold an election to unionize the workforce, what percentage of the workers must have signed authorization cards?

a. At least 25 percent.

b. At least 30 percent.

c. At least 50 percent.

d. none of the above.