In the equally tempered scale to which keyed instruments have been tuned since the days of J.S. Bach (1685-1750), the frequencies of successive notes $\mathrm{C}, \mathrm{C} \#, \mathrm{D}, \mathrm{D} \#, \mathrm{E}, \mathrm{F}, \mathrm{F} \#, \mathrm{G}, \mathrm{G} \#, \mathrm{A}, \mathrm{A} \#$
B, $\bar{C}$ form a geometric sequence (progression), with $\bar{C}$ having twice the frequency of $\mathrm{C}(\mathrm{C} \# \text { is read } \mathrm{C} \text { sharp). What is the ratio } r$ between the frequencies of successive notes? If the frequency of
$A$ is $440,$ find the frequency of $\bar{C}$