Calculating fees.

[FePe]

Merry christmas to everybody, I am new to OsComerce and I have a problem that is beyond my knowledge.

I am setting up a virtual store to sell films. The user selects the films and the phisical media (VHS, CD or DVD).

Option 1) VHS is selected (1 film per tape).

For 3 different films - VHS ($ 10 each) - Total = $30 + ship + ship + ship.

I have to send 3 tapes.

Option 2) CD is selected (2 films per CD).

For 3 different films - VHS ($ 10 each) - Total = $30 + ship + ship.

I have to sen 2 CDs.

Option 3) DVD is selected (4 films per DVD).

For 3 different films - VHS ($ 10 each) - Total = $30 + ship.

I have to send 1 DVD.

Where "ship" stands for shipping.

How do I calculate that, I have the sliggthest idea?

FePe.