Multiple questions about calculations

These questions are for a static page

1 .Our price increase for larger sizes is different for t-shirts ($3) than sweat shirts ($5). I’ve created both a tSize column (select list) and sSize column (select list). Ffrom other threads on the forum I’ve believe I would use the following calcs. But how do I combine the two into one calculation (what does “?[Price]” mean?

(abs([tSize] == '2XL' || [tSize] == '3XL'))?[Price] + 3:[Price]
(abs([sSize] == '2XL' || [sSize] == '3XL'))?[Price] + 5:[Price]

2. I would like to provide for the option of Pickup or Shipping via a select list, how would I go about doing this either by item or total order, whichever is easiest/preferred?

3. How can I prevent the selection of the shipping option for orders placed from outside the US (we can’t handle the shipping)

4. How can I limit the quantity of each item?

5. The cart will include some items that have PayPal fees and some that do not, how can I accommodate that?

6. How do I include the calculation of PayPal (standard) fees including the extra percent charged on orders placed outside the US.

Thanks,
Dennis