Thank you for your advice so far, and I have been attempting to understand where I am going wrong. Below is my latest attempt. I am using both if..else and switch, but am not sure if I have set the costs in the best way. Also it does not end the right way on some selections. It is going back to the earlier question on extras.
I guess my two questions here are, how should I be incorporating the else part so the total cost is delivered at the end? And secondly, is there a better way to establish those costs in the first place?