Let $\mathbb{F}[z]$ denote the vector space of all polynomials having coefficient over $\mathbb{F}$, and define $U$ to be the subspace of $\mathbb{F}[z]$ given by
$$
U=\left\{a z^{2}+b z^{5} \mid a, b \in \mathbb{F}\right\}
$$
Find a subspace $W$ of $\mathbb{F}[z]$ such that $\mathbb{F}[z]=U \oplus W$.