Static Methods: Exercise 3

Write a program that determines the alpha grade for 
a specific final grade (using the Sheridan grading system,
see table below)

- ask the user for a final grade
- include a method getAlpha() that accepts the final 
  grade and returns an alpha grade 
- display the alpha grade for the final grade entered

Range           Alpha
90 and higher   A+
85, up to 90    A
80, up to 85    A-
75, up to 80    B+
70, up to 75    B
65, up to 70    C+
60, up to 65    C
55, up to 60    D+
50, up to 55    D
below 50        F