Given the data from the Fluorescence, Quenching, and DNA experiment:

$$

Solution

Component

$$A $($No DNA$)$

B

C

D

E

F

$$G $($high DNA$)$

DNA, $$M

$0\mathrm{.}0$

$3\mathrm{.}10$

$4\mathrm{.}70$

$6\mathrm{.}20$

$9\mathrm{.}30$

$11\mathrm{.}0$

$17\mathrm{.}0$

Proflavine, $$M

$1\mathrm{.}35$

$1\mathrm{.}35$

$1\mathrm{.}35$

$1\mathrm{.}35$

$1\mathrm{.}35$

$1\mathrm{.}35$

$1\mathrm{.}35$

Fluorescence

Intensity

$118\mathrm{.}3$

$78\mathrm{.}6$

$59\mathrm{.}4$

$43\mathrm{.}4$

$36\mathrm{.}5$

$22\mathrm{.}7$

$7\mathrm{.}7$

What is the concentration, in $$M$,$ of free proflavine in solution D$?$ Report the answer in decimal format to three places after the decimal point. Do not include units.