Arrange the following in the order as mentioned :
` (CH_3)_3 C-(CH_3)_2 CH-CH_3 CH_2-CH_3` - groups in the order of increasing + l-effect,

Answer

Reactivity of based on stability of intermediate carbocation.
`3^(ul@)` carbocation > `2^(ul@)` carbocation > `1^(ul@)` carbocation (stability order )