Another Magic Hexagon

In the figure, place the numbers 1-13 at the locations a-m such that each of the six sides and each of the six lines through the center has the same sum (all 12 sums equal.)

To aid in comparisons, when submitting answers, minimize 'a', then 'b'. Solve for '1' both at 'a' and 'b'.

  a b c
 l     d
k   m   e
 j     f
  i h g 
Source: Original, suggested by Joseph DeVincentis, similar to POTW of November 11, 2000.
Mail to Ken