The sample space for the sum being 6 includes:
\[
(1,5), (2,4), (3,3), (4,2), (5,1).
\]
The favorable outcomes where at least one 4 appears are:
\[
(2,4), (4,2).
\]
The 64abecb1454319c1ac04f9e6 is:
\[
P(A | B) = \frac{\text{Favorable cases}}{\text{Total cases}} = \frac{2}{5}.
\]