7 The multiplicative group \(G\) has eight elements \(e , a , b , c , a b , a c , b c , a b c\), where \(e\) is the identity. The group is commutative, and the order of each of the elements \(a , b , c\) is 2 .
- Find four subgroups of \(G\) of order 4.
- Give a reason why no group of order 8 can have a subgroup of order 3 .
The group \(H\) has elements \(0,1,2 , \ldots , 7\) with group operation addition modulo 8 .
- Find the order of each element of \(H\).
- Determine whether \(G\) and \(H\) are isomorphic and justify your conclusion.