Pokemon petting zoo tickets

Tags
Challenge
No

Compute the price of tickets to a Pokemon petting zoo. Make a form like this:

Form

Users enter the number of adults and kids in their group. Assume users always input numbers that are zero or more. For example:

Input

Show the price, where adult tickets are $15, and kid tickets are $8.

Output

If adults is zero, and kids is more than zero, show an error message.

Bad input

Error

Submit your solution URL, and a zip of your files. The usual coding standards apply.

Where referenced