The Value of the Conference Board Index of 10 Economic $$E ( t ) = \left\{ \begin{array} { l l } 0.4 t + 110 & \text { if } 6 \leq t \leq 15 \\- 0.2 t 119 & \text { if } 15 < t \leq 20\end{array} \right.$$

The value of the Conference Board Index of 10 economic indicators in the U.S. could be approximated by the function of time t in months since the end of December 2002. $$E ( t ) = \left\{ \begin{array} { l l } 0.4 t + 110 & \text { if } 6 \leq t \leq 15 \\- 0.2 t 119 & \text { if } 15 < t \leq 20\end{array} \right.$$
Use the model to estimate when - prior to March, 2004 - the index was 113.

A) $t = 7.0$ months
B) $t = 7.5$ months
C) $t = 7.8$ months
D) $t = 7.4$ months
E) $t = 6.5$ months