3. Use EBNF notation to describe the syntax of the following language constructs. (a) A Java return statement, which could be either a return keyword followed by a semicolon, or a return keyword followed an expression then followed by a semicolon. Assume the grammar for expression has been defined as expr-> (b) A Python return statement, either a return keyword, or return one or more expressions separated by comma. (c) Based on your syntax definition in (b), is return x+y; a valid Python return statement? 4. Use the virtual machine codes (format shown below) to describe the operational semantics of the following C++ statements. Virtual machine code format: (id here refers to any identifier/variable.) id1 = id2 id = id1 op id2 (here op could be any arithmetic or logical operator.) goto label if id1 relop id2 goto label (here relop could be any relational operator) total = 0; for (int i=0; i<>