Write an applet that is a simple stack-based calculator. The calculator should have a text field where you can enter a double number and a text area that displays a stack of numbers. There should be an enter button that reads the number from the text field and pushes this number onto the stack. There are also several buttons for operations such as +, –, *, and /. When an operation button is pressed, the top two numbers are popped off the stack, and the operation is applied. The first number popped is always the second operand.