Business Math Assignment - Urgent!

Hi my name is Tanya and I require some math help on one of my assignments:

1. A loan arrangement carrying a fluctuating rate of interest and which can be terminated at any time by either borrower or lender is called a ___________?

2. What is the maturity date of a 90 day debt incurred on September 4th?

3. Calculate the interest payable on a 60 day promissory note for $450 if the rate is 12% and the note is signed on July 2nd.

4. What will be the amount payable on the legal due date of a 6 month promissory note for $3,000 signed on August 22nd with interest at 13 percent?

I hope someone is able to not only provide me with an answer but also an explanation on how they got these answers. It is greatly appreciated as I will require myself to know how to do it for my test. I look forward to hearing from someone and thanks again.

Cheers :)

Tanya