y   method oper assem workplace
11    C     1     1       b
8     B     1     2       a
9     A     1     3       d
9     D     1     4       c
10    B     2     1       c
12    C     2     2       d
11    D     2     3       a
8     A     2     4       b
14    D     3     1       d
10    A     3     2       c
7     B     3     3       b
18    C     3     4       a
8     A     4     1       a
12    D     4     2       b
15    C     4     3       c
6     B     4     4       d
