Answer:
Depends on assumptions, likely 39.00 or 32.50, read below
Explanation:
'Pack' implies (at least to me) that those 6 shirts are sold as a unit and you are not allowed to break them up. If this is true and you have to buy 2 packs (12 shirts) to end up with at least 10, then the price would be 2 * 19.50 = 39.00
If this assumption is NOT true and you are allowed to buy shirts individually at no penalty, then one shirt in a 6 pack costs 19.50 / 6 = 3.25 per shirt, so 10 shirts would be 32.50.
If packs can be broken up, but at a penalty, then it would depend based on the extent of the penalty. Let's say a 6-pack is 19.50 and individual shirts are 3.50 each, then 10 shirts would be a 6-pack plus 4 individual 19.50 + 4(3.50) = 33.50 (I'm picking the cost of an individual shirt out of thin air, so I doubt this option is the 'right' answer)