Help getting my syntax correct

I am calculating shipping charges in Excel 2007.

A1 is a drop down box with two options: Standard shipping and Priority Shipping.

I need to calculate based on two conditions:

If "Standard Shipping" is selected and the # of items (B1) is <=5, then the shipping charge (C1) = $5.00.

I need to nest this for 4 different values for B1 AND for Standard Shipping and Priority Shipping. I could also use two check boxes instead of the drop down if that would be better.

I just can't seem to get it right.