A massive, uniform, flexible string of length L is placed on a horizontal table of length L / 3 that has a coefficient of friction \mu_{s}=1 / 7, so equal lengths L / 3 of string hang freely from both sides of the table. The string passes over the edges of the table on smooth, frictionless, curved surfaces. Now suppose that one of the hanging ends of the string is pulled a distance x downward, then released at rest. Neither end of the string ever touches the ground in this problem. The maximum value of x so that the string does not slip off of the table is
Answer Choices
A. L / 42
B. L / 21
C. L / 14
D. 2 L / 21
E. 3 L / 14