1. Write a function that calculates the volume of a sphere using the formula ''4/3*pi*''r''^3^''. What is the volume of a sphere with radius of 5?

Hint 1: The module {{{math}}} has a field called {{{pi}}}.

Hint 2: The answer is ''not'' 392.70.

2. Write a function that takes a list as argument and returns a list of unique elements from the original list. 

3. Create a dictionary {{{D}}} with keys {{{a}}}, {{{b}}}, and {{{c}}}. What happens if you try to index an nonexistent key {{{d}}} ({{{D[d]}}})? Whath appens if you try to assign a nonexisting key d (e.g. {{{D[d] = 'spam'}}})?

4. Write a {{{for}}} loop that prints a dictionary's items in sorted (ascending) order. 

Hint: Use dictionary {{{keys}}} and the list {{{sort}}} method.

5. Write a function, {{{copyDict(dict)}}} that copies a dictionary. It should return a new dictionary with all items in its argument.