Consider the set H of all 3 x 3 matrices of the type
a f e
O b d
O O c
where a,b,c,d,e and f are real numbers and abcO. under the matrix
multiplication operation, the set H is:
option
(a) a group
(b) a monoid but not a group
(c) a semi group but not a monoid
(d) neither a group nor a semi group