The flash unit on a camera operates by storing charge on a capacitor and releasing it suddenly when the flash is set off. The following data describe the charge $Q$ remaining on the capacitor (measured in microcoulombs) at time $t$ (measured in seconds).

$$\begin{array}{|c|c|} \hline t & Q(t) \\ \hline 0.00 & 100.00\\ 0.02 & 81.87 \\ 0.04 & 67.03 \\ 0.06 & 54.88 \\ 0.08 & 44.93 \\ 0.10 & 36.76 \\ \hline \end{array}$$
(a) Use a graphing calculator or computer to find an exponential model for the charge (to the nearest millionth).
(b) The derivative $Q'(t)$ represents the electric current (measured in microamperes) flowing from he capacitor to the flash bulb. Use part (a) to estimate the current when $t=$.04 s to the nearest hundredth.

(a) $Q(t) =$
(b) $Q'(.04) =$ $\mu$A.