So, we were asked to design a vending machine. You can insert nickles, dimes, quarters, and dollars. I can add the amounts up, my only problem is that I can't get the input correct.
My circuit is attached as a jpeg.

Here are my questions. Any help is much appreciated. By the way, I am currently on hour 12 of trying to design this circuit.

1) in the 6-bit rate multiplier - Is this a 3bit x 3 bit multiplier? If not, what does it do.

2) in the bottom is a BCD counter hooked up to a 7seg display. It only increments in threes. I have tried playing with the inputs (using switches instead of looping the 7seg output back around), but it doesn't seem to make a difference.

3) (Only if you're bored and feel like helping a desperate student) What method would you use to approach this. I have talked to some of the other students in my class and they say they used a series of selectors and registers. Well from my understanding isn't the series of t flip-flops I have already a register?

What I would suggest is download a program called LTspice and insert the circuitry into LTspice where you may perform tests to find out all of the answers. :)