BCDE is a Rhombus. BD=28, and CE=20 what is ED. ?

Given:
BCDE is a Rhombus.
[tex]BD=28\text{ ; CE=20}[/tex]Let 'a' be the side of a rhombus.
[tex]\begin{gathered} a=\frac{\sqrt[]{BD^2+CE^2}}{2} \\ a=\frac{\sqrt[]{28^2+20^2}}{2} \\ a=\frac{\sqrt[]{784+400}}{2} \\ a=\frac{\sqrt[]{1184}}{2} \\ a=17.2 \end{gathered}[/tex][tex]ED=17.2[/tex]Option d is the final answer.