I.
Develop a module that will replace the default "minimum order amount required" to have different "minimum amount" depending on country zones.

For example:
a minimum of 20euro for Athens (Greece),
a minimum of 30euro for the rest of the Greece,
a minimum of 40euro for all other countries.

If the user cart amount is smaller than the minimum required, then to have a popup with a message like:
"The minimum order for "The country/zone" (e.g Athens) is 20€ so please add more products to your cart".

The prestashop version is 1.6.1.5 (the latest stable)
II.
Currently, prestashop allows to set only 1 minimum amount required as image below
Backend setting
Front end 
We will build a friendly module to allow admin to set minimum amount required for each zone of country and for other countries as well
On frontend, when customer add products to cart and go checkout, at payment method step, we will show message if the order amount is not reached minimum amount required which is based on address of customer
III. 
After discussing carefully with my team, our best price for doing this job is 350 USD
IV.
Time frame: 3-5 days (12th May 2016 - 17th May 2016)