Plz explain how APR works!

[Dennis Smith]

Guys hi

I want to take credit line from my bank(chase)

just spoke with my business banker and she said that i can count on 10%-15% APR.

I am looking to get 30K credit line.

How do the interest and payments calculated?

Let's say i am approved for 30K with 12% APR.

On Feb 1st i spend ALL this money(30K) on inventory i want to buy.

What will be the interest and payments? The interest won't be 30,000*0,12 every month right? It will be 30,000*0,12 TOTAL for a year, right?
And if i pay this within 6 months it will be even less. Basically total amount i will end up paying will be 30.000K i took + around 2.2K in interest - does i calculate it right?

It's totally new for me, so please explain in details:)

Thx a lot! bTycoon

p.s. i already have 2 business credit cards(chase and amex), just want to get credit line(expect to pay it withing 6 months most) for inventory.