//chapter28
//example28.13
//page609

printf(" Y = ( A` + B ) . ( A + B ) \n")
printf(" By theorem 15 \n")
printf(" Y = A` . A + A` . B + B . A + B . B \n")
printf(" By theorem 4 and 6 \n")
printf(" Y = 0 + A` . B + B . A + B \n")
printf(" Y = A` . B + B . A + B \n")

printf(" By theorem 14 \n")
printf(" Y = B . ( A` + A + 1 ) \n")
printf(" By theorem 7 \n")
printf(" Y = B . ( A` + 1 ) \n")
printf(" By theorem 7 \n")
printf(" Y = B . 1 ) \n")
printf(" By theorem 2 \n")
printf(" Y = B \n")