(1) a b c d  (ab + c)  (a + b' + d)  (a'c + bd)  (a' + b' + c')
    -------  --------  ------------  ----------  --------------
    0 0 0 0
    0 0 0 1
    0 0 1 0
    0 0 1 1
    0 1 0 0
    0 1 0 1
    0 1 1 0
    0 1 1 1
    1 0 0 0
    1 0 0 1
    1 0 1 0
    1 0 1 1
    1 1 0 0
    1 1 0 1
    1 1 1 0
    1 1 1 1


(2) ab\cd | 00 01 11 10
    ------+------------
    00    |            
    01    |            
    11    |            
    10    |            


(3)