If Roxie were to buy the cereal bars individually, it would be
38 x $2.40 = $91.20
If she were to buy them in packs, she would need to buy 9 packs along with 2 individual bars (because there are 4 in each pack, 4x9=36 and adding 2 more would make it 38)
9 x $8 = $72
2 x $2.40 = $4.80
$72 + $4.80 = $76.80
The least amount of money Roxie can spend is $76.80 by buying the cereal bars in packs.