b

    60    40    30    30    40    40    40    30     0
    40     0   -10   -10     0     0    10     0   -30
    40   -10   -30   -30   -20   -20     0   -10   -40
    30   -30   -30   -10     0     0    20     0   -40
    10   -30   -10    10    10     0    20     0   -40
    10   -10     0    10     0   -10    10   -10   -40
    30    10    20    10   -10   -10    10    10   -20
    30     0    20     0   -10    10    20    20   -20
   -10   -40   -20   -40   -40   -10   -20   -30   -50