What is the 4th term of the geometric sequence 12,38,932,...\frac{1}{2}, \frac{3}{8}, \frac{9}{32}, ...21,83,329,...?
27128\frac{27}{128}12827
27256\frac{27}{256}25627
964\frac{9}{64}649
81512\frac{81}{512}51281