In the Circuit Shown, Both Resistors Have the Same Value $\tau$

Multiple Choice

In the circuit shown, both resistors have the same value R. Suppose switch S is initially closed. When it is then opened, the circuit has a time constant $\tau$ _a Conversely, suppose S is initially open. When it is then closed, the circuit has a time constant $\tau$ _b The ratio $\tau$ _a/ $\tau$ _b is:

A) 1
B) 2
C) 0.5
D) 0.667
E) 1.5