To determine which box size is NOT a viable option, we need to check which sizes evenly divide into 28.
- 4 cupcakes per box: \(28 \div 4 = 7\) (viable)
- 7 cupcakes per box: \(28 \div 7 = 4\) (viable)
- 10 cupcakes per box: \(28 \div 10 = 2.8\) (not viable)
- 14 cupcakes per box: \(28 \div 14 = 2\) (viable)
The box size that is NOT a viable option is 10 cupcakes per box.