OAEF is a rectangle, ABCD is a square
$| \mathrm { FE } | = 7$ units
$| \mathrm { AB } | = 2$ units
$| \mathrm { DE } | = x$
In the figure, points E and C are on a quarter circle with center O.
Accordingly, what is $x$ in units?
A) $\frac { 7 } { 2 }$
B) $\frac { 9 } { 2 }$
C) $\frac { 13 } { 4 }$
D) 3
E) 4