The Table Below Shows Hypothetical Per- Minute Cell Phone Charges

The table below shows hypothetical per- minute cell phone charges for "pay- and- talk" service over several years. $$\begin{array}{l}\begin{array} { | l | l | } \hline 2005 & 0.55 \\\hline 2006 & 0.50 \\\hline 2007 & 0.40 \\\hline 2008 & 0.35 \\\hline 2009 & 0.25 \\\hline\end{array}\\\text { TABLE 2- } 2\end{array}$$
-Refer to Table 2- 2. Assume that 2005 is used as the base year, with the index number = 100. The value of the index number in 2007 is

A) 1.375
B) 137.5
C) 0.72
D) 72.73
E) 100