In "MP1.hs" you'll find the functions p1_ex1, p1_ex2, p1_ex3, and p1_ex4, all of which are defined but lack type declarations. Add a valid type declaration before each function definition. If you have a choice, make the type declaration as general as possible --- i. e., prefer polymorphic to monomorphic types, adding class constraints when necessary. Ensure that your code compiles (i. e., gets past the type-checker). Use a, b, c, ..., for type variable names.
Note that is trivial to "cheat" at this part by using the :t command in GHCi, or just reading compilation errors. Please try to do this without help from GHCi or the compiler --- it's good practice! You can always double-check your work afterwards.