Pong (Horray...)

I’ve got a basic version of pong up and running, but I can’t figure out how to reset the ball back to it’s original speed every time a point is scored, also i can’t seem to increase the computer opponent lag to make the game possible to win. Anyhelp would be greatly appreciated.

Mouse.hide();
bounce = 1
vx = Math.random()*5+2;
vy = Math.random()*5+2;
top = 0;
bottom = 300;
left = 0;
right = 500;
playerscore = 0;
computerscore = 0;
ball.onEnterFrame = ballMove;
playerpaddle.onEnterFrame = playerMove;
computerpaddle.onEnterFrame = computerMove;
function ballMove() {
this._x += vx;
this._y += vy;
if (this._y<top) {
this._y = top;
vy *= -bounce;
}
if (this._y>bottom) {
this._y = bottom;
vy *= -bounce;
}
if (this._x<left) {
this._x = left;
vx *= -bounce;
}
if (this._x>right) {
this._x = right;
vx *= -bounce;
}
if (this.hitTest(playerpaddle)) {
vx *= -bounce;
vy *= -bounce;
}
if (this.hitTest(computerpaddle)) {
vx *= -bounce;
vy *= -bounce;
}
if (this._x<=5) {
this._x = 250;
this._y = 150;
playerscore++;
}
if (this._x>=495) {
this._x = 250;
this._y = 150;
computerscore++;
}
}
function playerMove() {
this._y = _ymouse;
}
function computerMove() {
this._y = ball._y;
}