[Discrete Mathematics]

Can someone please explain and help me understand this problem?

3. Let fand g be functions from (1,2,3,4) to (a, b, c, d) and from fa, b, c, d to 1,2,3,4), respectively, with f(1) = d, f(2) = c, f(3)-a, and f(4) = b, and g(a)= 2, g(b)= 1, g(c)-3, and g(d)= 2. a. What is (f og)(b)?d b. What is the domain of (fog)? 2 c. What is the co-domain of (fog)? a hCV4[ad] d. What is the image set ("range") of(fog)? 4yed e. Which function(s) is bijective, rco f. Which functions(s) has an inverse? g. Find the function inverse(s): 2. Domain