How do you do these three parse trees?

I const I ( expression ) Using the grammar on the previous page derive the following sentences, and draw a parse tree for the sentences. The start symbol is . If any sentences cannot be formed by the grammar state why and show the derivation and parse tree until the error. 1 a. f (f+a - b) / (f- a b) 2. Tell me the order of operator precedence in the grammar. 3. Is this grammar ambiguous? If it is explain what need to be changed to make it unambiguous