Driving at a constant speed, Sharon usually takes 180 minutes to drive from her house to her mother’s house. One day Sharon begins the drive at her usual speed, but after driving \dfrac{1}{3} of the way, she hits a bad snowstorm and reduces her speed by 20 miles per hour. This time the trip takes her a total of 276 minutes. How many miles is the drive from Sharon’s house to her mother’s house?
Answer Choices
A. 132
B. 135
C. 138
D. 141
E. 144