LIST I | LIST II | ||
|---|---|---|---|
| A | Thickness of head | I | d |
| B | Threaded length of shank | II | 0.8d |
| C | Radius of are showing conventional end of the shank in its front view | III | 2d+6 |
| D | Width across the flats of head | IV | 1.5 d+3 |
What comes next in the series?
\(2, 6, 12, 20, 30, \ ?\)