Answer:
In Python:
def num_to_letter(num):
  if num == 5:
    grade = "A"
  elif num >= 4.0:
    grade = "B"
  elif num >= 3.0:
    grade = "C"
  elif num >= 2.0:
    grade = "D"
  else:
    grade = "E"
  return "Grade is "+grade
Explanation:
This defines the function
def num_to_letter(num):
If num is 5, grade is A
  if num == 5:
    grade = "A"
If num is 4 to 4.9 , grade is B
  elif num >= 4.0:
    grade = "B"
If num is 3 to 3.9, grade is C
  elif num >= 3.0:
    grade = "C"
If num is 2 to 2.9, grade is D
  elif num >= 2.0:
    grade = "D"
For 0 to 1.9, grade is E
  else:
    grade = "E"
This returns the grade
  return "Grade is "+grade