Solution

1. \([\mathrm{high}]_o(x)=[\mathrm{high}]_o(x)\)
2. \([\mathrm{low}]_o(x)=[\mathrm{low}]_o(x)\)
3. \([\mathrm{nasal}]_o(x)=[\mathrm{nasal}]_o(x)\)
4. \([\mathrm{ATR}]_o(x)= \begin{array}[t]{l} \mathtt{if}~[\mathrm{low}]_i(x)~\mathtt{then}~\top~\mathtt{else}\\ \mathtt{if}~[+\mathrm{ATR},+\mathrm{hi}]_i(s(x))~\mathtt{then}~\top~\mathtt{else}\\ \mathtt{if}~[+\mathrm{ATR},-\mathrm{hi},-\mathrm{lo},-\mathrm{nas}]_o(s(x))~\mathtt{then}~\top~\mathtt{else}\\ [\mathtt{ATR}]_i(x) \end{array} \)