4. [10 points] Write a program which will do the following: a) Show how to declare a tag named complex for a structure with two members, real and imaginary of type double. b) Use the complex tag to declare variables named cl, c2, and c3. c) Write a function named make_complex that stores its two arguments (both of type double) in a complex structure, then returns the structure. Note: The function declaration for the make_complex function looks like struct complex make_complex(double real, double imaginary); d) Write a function named add_complex that adds the corresponding members of its arguments (both complex structures), then returns the result (another complex structure). Note: The function declaration for the add_complex function looks like struct complex add _complex(double real, double imaginary); 5. [8 points] Write a program that reads a message, then checks whether it is a palindrome (the letters in the message are the same from left to right or right to left) or not. You must use dereferencing of pointers to read the input message stored in a character array. Ignore all characters that are not letters. Use integer variables to keep track of positions in the array. 6. 4 points] Suppose that the direction variable is declared in the following way: enum (NORTH, SOUTH, WEST, EAST) direction; Let x and y be int variables. Write a program which declares an enumeration type data structure as given above, and then declares variables x and y of type enum. Then write a switch statement that tests the value of direction, incrementing x if direction is EAST, decrementing x if direction is WEST, incrementing y if direction is SOUTH, and decrementing y if direction is NORTH