You will be given several functions and asked to indicate whether f1 & f2 & f3 & f4 are 1-1 or onto (or both, or neither). Please show the process.

f1: {a,b} x {0,1} --> {w,x,y,z} defined by f1(a,0) = z f1(a,1) = y f1(b,0) = w f1(b,1) = x

f2: {a,b} x {0,1} --> {w,x,y,z} defined by f2(a,0) = x f2(a,1) = y f2(b,0) = w f2(b,1) = x

f3: {u,w,x,y,z} --> {a,b} x {0,1} defined by f3(u) = (a,1) f3(w) = (a,0) f3(x) = (b,0) f3(y) = (b,1) f3(z) = (a,1)

f4: {x,y,z} --> {a,b} x {0,1} defined by f4(x) = (a,0) f4(y) = (b,0) f4(z) = (b,1)