Slitherlink Septistar Mystery Cache

This tiling was a new one on me (discovered when looking for tilings I had not used in the series so far). It is called septistar as the tiling has a seven pointed star at its heart.

To work out the location of this cache, you need to do the following:

1. Solve the puzzle below (see the cache listing for Slitherlink Boot Camp for the rules about how to solve Slitherlink puzzles).
2. Locate the letters a through to u in the puzzle (i, l and o are omitted). For each letter, its numeric value is the number of lines around the cell.

The cache can be found at S 43 31.ABC E 172 33.DEF, where:

A = a + b - c
B = d + e + f
C = g + h + j
D = k + m + n
E = p + q + r
F = s + t + u

The checksum for A to F is 37.

The cache is a pill bottle inside another round container, tucked away in ivy about ankle height behind a fence post. Can be reached from the grass (no need to go into the shrubbery).