Each of the following carbocations can rearrange to a more stable ion. Propose structures for the likely rearrangement products.
(a) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2}^{+} \quad$ (b) $\mathrm{CH}_{3} \mathrm{CH}^{+} \mathrm{CHCH}_{3}$
$$
\mathrm{CH}_{3}
$$