Which of the following iodoalkanes would more readily undergo an S _N1 reaction? Why?

Iodoalkane (a) will react more readily due to the formation of a more stable tertiary carbocation.

Iodoalkane (b) will react more readily due to the formation of a more stable secondary carbocation.

Iodoalkane (a) will react more readily due to the formation of a more stable secondary carbocation.

Iodoalkane (b) will react more readily due to the formation of a more stable tertiary carbocation.