The production rules of a grammar for simple arithmetic expressions are:
$$\langle\text { expression }\rangle :=\langle\text { digit })(\langle\text {
expression })) |+(\langle\text { expression }\rangle) |$$
$$-(\langle\text { expression }\rangle) | \langle\text { expression }\rangle
\langle\text { operator }\langle\text { expression }\rangle$$
$$\langle\text { digit }\rangle : := 0|1| 2|3| 4|5| 6|7| 8 | 9$$
$$\langle\text { operator }\rangle : :=+|-| / | \uparrow$$
Use this grammar to answer Exercises \(52-59\).
Determine if each is a valid arithmetic expression.
$$3+\uparrow 7$$