11.Let X={1,2,3,4,5} and Y={a,b,c,d}. Let f:XY be the tuilowing function: f(1)=b,f(2)=d,f(3)=a,f(4)=c,f(5)=b. Is f (a) one-to-one; (b) onto; (c) what is f1(B), where B={a,b}. 12.Determine whether the mapping f:RR,f(x)=5x+1, is one-to-one and onto