title: unsure how to unwrap uilabel optional to calculate my to uilabels
body: <p>I am new in the developer world and have been on and off since february with swift and Xcode. I am hoping someone could help me out. Im trying to make a simple tip calculator and can't  seem to * two uilabels together. this is what i have so far... at the total.text = "(totalAmount) * (tipPercent)" ... thanks any help would be great. :)</p>
  
  <pre><code>@IBOutlet weak var totalAmount: UILabel!
  @IBOutlet weak var textFIeld: UITextField!
  @IBOutlet weak var tipPercent: UILabel!
  @IBOutlet weak var slider: UISlider!
  @IBOutlet weak var total: UILabel!
  @IBOutlet weak var tip: UILabel!
  
  
  @IBAction func sliderChanged(_ sender: UISlider) {
      sldr()
  
      total.text = "\(totalAmount) * \(tipPercent)"
  }
  
  
  @IBAction func buttonPressed(_ sender: Any) {
      ttl()
  }
  
  func ttl() {
      if let grandTotal = textFIeld.text {
          totalAmount.text! = "\(grandTotal)"
      }
  }
  
  func sldr() {
      tipPercent.text! = "\(Int(slider.value))"
  }
  </code></pre>