MD writes an order for Robitussin AC 100 mg by mouth 3 times per day as needed for cough. Pharmacy dispenses you with 100 mg/5 ml. How many teaspoons will you administer per dose?

a. 0.5 tsp/dose
b. 1 tsp/dose
c. 2.5 tsp/dose
d. 3 tsp/dose