$(function() {
    var submitObject = $('#submit');
    var imageObject = submitObject;
    if (!imageObject.attr('src')) {
        imageObject = $('#submit img');
    }

    var buttonFile = imageObject.attr('src');
    if (!buttonFile) {
        return;
    }

    var hoverButtonFile = buttonFile.replace(/\.png/, '') + '-hover.png';

    submitObject.hover(
        function() {
            imageObject.attr('src', hoverButtonFile);
        },
        function() {
            imageObject.attr('src', buttonFile);
        }
    );
});