a) The first option is that you enter to the Setup screen of the application (press the Settings button that appears on the main screen at the bottom right) and then check if the sound option are turn ON. If this does not enough, try the next option.
b) Another option that exists is that you can have a mute button of device activated, disable it and retry. If the problem persist please try the next one.
c) We will have to delete the application and reinstall it. Do not worry about the payment, you will not charge anything, and that payment is made only once. To delete it, you stay just pressing the application icon until it starts to “shake”, and then reinstall it, entering the AppStore, search for “Lee Step by Step” and reinstall. Be sure to do it with the same iTunes account that purchased it. After all please reenter into the game and review it.