4. [30 points] The following context-free grammar G is ambiguous. Give an equivalent unambiguous grammar . The terminal alphabet of G is {a, b, c, (.), +,-, *). G has only one variable, narnely the start symbol E. The productions of G are as follows: (a) EE+E (b) EE-E (c) EB+E (e) E-ta (f) E b (g) E c