Need help with product prices + options

The site i'm setting up has different options for purchasing, and i'm not sure how to set them up.

• If they are purchasing the products (all products) in our home city - no shipping fee.
• If they are purchasing over $100.00 worth of products (all products), no shipping fee.
• If they are purchasing over $100.00 worth of a specific product, the price of the product drops. So if an item is $50.00, if someone buys 4 of them the price goes to $40.00 for each item.

Any help on how to do those?

Thanks.

I figured out how to do the free shipping if the products are over 100$.

Is there a way to do free shipping inside a specific zone (City) and lowering the price if a certain amoutn of a single product are bought?