In a box that is 12 x 9 x 7 how many 35 hour heat packs should I use on a 40 degree day. The snake is being delived Delta Dash, and will be in transit for about 4-6 hours.

Thanks!
-----
---------
4.16 Normal ball pythons
2.0 Pastel ball pythons
1.0 Plains Garter
0.1 Normal Kenyan Sand Boa
1.1 Anery Kenyan Sand Boa
1.0 Mid-Baja Rosy Boa
0.1 Leucistic Texas Rat
1.2 Dumeril's Boa
-----My list is too long, so I'll stop here!
*Amy*