The question is:
Let S, T and U be sets and let a and b be mappings from S to T and from T to U respectively. Assume that the mapping a is not onto.
a) Give an example of sets S, T and U and mappings a and b, such that b o a is onto.
b)Can the mapping b o a be invertible, and, if yes, which additional properties do a and b possess?
c)If the answer to (b) is yes, give examples of sets S, T and U and of mappings a and b for which b o a is invertible and for which it is not. (the answer to (a) may be one of the examples. The sets s, T and U need not be the same as in (a))
Can anybody help with one please?
Thanks in advance