Not understanding how to solve this problem

5. The following is a description for "JH-Lisp", which is the language previously described in homework 2, problem 5, with a slight modification. An operator is one of the characters + - */ A number is any sequence of one or more of the digits 0-9 (example: 42) A list expression is defined as an open parenthesis C, followed by an operator, followed by a space, followed by exactly two expressions (separated by a space) and terminated by a close parenthesis ")". An expression is defined as either a number or a list expression. A valid string in JH-Lisp is a list expression. An example string in the language is as follows: (+ (- 25 4) (* (1 40 10) 3)) Give a context-free grammar for JH-Lisp