If 500 mg of a certain medication is given to a patient, and the amount of the medication in the patient’s system is cut in half every hour, then amount A of medication in the patient’s system can be found using the formula A(t)=500(1/2)^t. About how long will it take to have less than 40 mg of the medication left in the patient’s body?

A. 3.7 hr
B. 1.4 hr
C. 6.1 hr
D 0.3 hour