Calculate Grade
===============

The grades of a given course must be calculated from 4 grades: three from partial exams (g1, g2, g3) and the grade from the final exam (gf). The value of any grade is a float value either between 0.0 and 10.0 (both included) or -1.0 if the student did not take the exam.

The grades from the 3 partial exams are used to calculate the *Continuous Evaluation Grade* (**CEG**) and the *Final Grade* (**FG**).

The **CEG** is calculated as the average of the **two best** partial grades (the worst is **discarded**). However, at least two of them have to be taken by the student, otherwise CEG is 0.0.

The **FG** is calculated as the maximum of CEG and gf, with the following exceptions:

    - If none of the 3 partial exams has been taken then FG will be 0.0.
    - If the final exam has not been taken the FG will be CEG. 

Please, implement using Python the function :func:`clc_grade` in the module :mod:`grade` (file :file:`grade.py`) according to the following specification:

    ``clc_grade(g1, g2, g3, gf)``
        | *takes*
        | ``g1, g2, g3, gf``, all them (let's call them gX) are a float value such that either `0.0 <= gX <= 10.0` or `gX == -1.0`
        | *returns* 2 values:
        | - a :class:`float` corresponding to the GEC calculated as specified above
        | - a :class:`float` corresponding to the *FG* calculated as specified above and rounded to 1 decimal.

For exemple:

   .. literalinclude:: clc_grade-test.txt
      :language: python3

Doctests are available at the :download:`clc_grade-test.txt` file.