I'm running a program that tracks the user's expenses. I've gotten most of it complete but need the most crucial part. When I run the program I get an error message of a1 not being defined. Here's what I have:

```
class Expense(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)

        home = Label(self, text = "Home: ")
        home.grid(row = 3, column = 0)
        util = Label(self, text = "Utilities: ")
        util.grid(row = 4, column = 0)
        health = Label(self, text = "Health/Medical: ")
        health.grid(row = 5, column = 0)
        food = Label(self, text = "Food: ")
        food.grid(row = 6, column = 0)
        transport = Label(self, text = "Transportation: ")
        transport.grid(row = 7, column = 0)

        a1 = Entry(self).grid(row = 3, column = 1)
        a2 = Entry(self).grid(row = 4, column = 1)
        a3 = Entry(self).grid(row = 5, column = 1)
        a4 = Entry(self).grid(row = 6, column = 1)
        a5 = Entry(self).grid(row = 7, column = 1)

        submit = Button(self, text = "Submit", command = self.AddExpenses)
        submit.grid(row = 8, column = 1)

    #Here's where I run an issue.
    def AddExpenses(self):
        expenses = [a1, a2, a3, a4, a5]
        total = 0
        for i in list:
            total = total + i
        print("Your total spent", total)

```