Imports System.Math
Imports System.IO
Module Module1
 Sub Main()
  Dim file As StreamWriter
  file = My.Computer.FileSystem.OpenTextFileWriter _
   ("C:\Users\Kevin C. Johnson\wwokt.txt", False)
  Dim ka As Double = 0
Repeat:
  Dim x As Double = 0
  Dim xmax As Double = 3.32
  Dim y(2) As Double
  y(1) = 1
  y(2) = 0
  Dim f(2) As Double
  Dim yn(2) As Double
  Dim kt As Double = 0.3012
  Dim kn1(2), kn2(2), kn3(2), kn4(2) As Double
  Dim h As Double = 0.0002
  Dim i As Integer
Start:
  For i = 1 To 2
   difeq(f, ka, kt, y)
   yn(i) = y(i)
   kn1(i) = f(i)
   x = x + h / 2
   y(i) = yn(i) + kn1(i) * h / 2
   difeq(f, ka, kt, y)
   kn2(i) = f(i)
   y(i) = yn(i) + kn2(i) * h / 2
   difeq(f, ka, kt, y)
   kn3(i) = f(i)
   x = x + h / 2
   y(i) = yn(i) + kn3(i) * h
   difeq(f, ka, kt, y)
   kn4(i) = f(i)
   y(i) = yn(i) + h * (kn1(i) + 2 * kn2(i) + 2 * kn3(i) + kn4(i)) / 6
   x = x - h
  Next
  x = x + h
  If x < xmax + h Then GoTo Start
  file.Write(ka.ToString("0.0000"))
  file.Write(" ")
  file.WriteLine(y(2).ToString("0.000000"))
  ka = ka + 0.035
  If ka < 3.5 Then GoTo Repeat
  file.Close()
 End Sub
 Sub difeq(ByRef f() As Double, ByRef ka As Double, ByRef kt As Double,
           ByRef y() As Double)
  f(1) = -(ka + kt) * y(1)
  f(2) = ka * y(1)
 End Sub
End Module