text: //cpp
  //include header file 
  #include "decision.h"
  #include <string>//to make string variable
  using namespace std;
  
  //write code for the functions using if
  string get_letter_grade_using_if( int num_grade)
  {
      string letter_grade;//create letter grade variable,needs to be string to return invalid entry
      if (90 <= num_grade && num_grade <= 100)//90<= numerical grade<=100
      {
          letter_grade= "A";//variable is assigned an A 
      }
      else if ( 80<=num_grade && num_grade< 90)//80<=numerical grade <90
      {
          letter_grade= "B";//variable is assigned a B
      }
      else if (70<=num_grade && num_grade< 80)//70<=numerical grade <80
      {
          letter_grade="C";//variable is assigned a C
      }
      else if (60<=num_grade && num_grade< 70)//60<=numerical grade <70
      {
          letter_grade="D";//variable is assigned a D
      }
      else if (0<=num_grade && num_grade< 60)//0<=numerical grade <60
      {
          letter_grade="F";//variable is assigned a F
      }
      else // numerical grade<0 or numerical grade >100
      {
          letter_grade="Invalid entry";//variable is assigned invalid entry
      }
      return letter_grade;//returns letter_grade value
  }
  
  //write code for functions using switch
  string get_letter_grade_using_switch(int num_grade)
  {
      string letter_grade;//create letter grade variable,needs to be string to return invalid entry
      switch (num_grade)//make a switch function within the get letter by switch function
      {
      case 90 ... 100://using 3 periods for a range, if numbers are or btw 90 & 100
          letter_grade="A";//variable is assigned a A
          break;//break allows it to go to next case if not btw range
      case 80 ... 89://if num grade is or btw 80 & 89
          letter_grade="B";//variable is assigned a B
          break;//break allows it to go to next case if not btw range
      case 70 ... 79://if num grade is or btw 70 & 79
          letter_grade="C";//variable is assigned a C
          break;//break allows it to go to next case if not btw range
      case 60 ... 69://if num grade is or btw 60 & 69
          letter_grade="D";//variable is assigned a D
          break;//break allows it to go to next case if not btw range
      case 0 ... 59://if num grade is or btw 0 & 59
          letter_grade="F";//variable is assigned a F
          break;//break allows it to go to next case if not btw range
      default://if num grade is greater than 100 or less than 0
          letter_grade="Invalid entry";//variable is assigned invalid entry
          break;//break allows it to go to next case if not btw range
      }
      return letter_grade; //returns letter grade variable
  }