A tertiary butyl carbocation is more stable than a secondary butyl carbocation because-

1. + R effect of ${CH}_3$ groups 

2. $-$R effect of $-$ CH₃  groups 

3. Hyperconjugation 

4. $-$l effect of $-$CH₃ groups 

The most stable carbocation among the following is:

1.		2.
3.		4.