Skype number cost with subscription?

I’m considering buying a Skype number because cell phone service in my room is so awful that I want to forward it to Skype for clear talking. However, the details on the cost of this service are very unclear on the website. They mention up to 50% off with a subscription, but they don’t say which subscription gives me 50% off. Here’s what I want to know:

How much will the number cost for the period equivalent to the following subscriptions:
a) 1 month (US&CAN = $2.95) I think a number isn’t possible for only one month.
b) 3 months (US&CAN = $8.40) Base price for number is $18.
c) 12 months (US&CAN = 30.05) Base price for number is $60.