The internal \(d_i\) and external \(d_o\) diameters of a Shelby sampler are 48 mm and 52 mm, respectively. The area ratio (\(A_r\)) of the sampler (in %, round off to two decimal places) is _______________
What comes next in the series?
\(2, 6, 12, 20, 30, \ ?\)