Please help me with this question, correct answer will get many upvotes, thank you

Design CFGs for the given languages: (a) Write a grammar that describes the strings (8)*(7|4)+. (b) Write a grammar that describes all the palindrome strings on the alphabet (terminals) of a, b and c. See the examples of valid strings; aca, bab, abba, acccca.. (c) In most programming languages, array elements can be represented using a name followed by any number of indices. The name might be a letter selected between ' a ' to ' z ', and an index can be represented using '[' integer ']'. For example, a[-9], b[10][1], c[0][1][2] are valid array elements. *Write a grammar to describe such array elements.|