Please help! Write a C function int atby(char t[]. char s[) that takes a string of length less than 100 (but not known) in array s, and replaces each instance of the word \"at\" with the word \"by\". Your function should not modify the original string in array s, but make a new copy in the array t supplied by the calling program. Your function should return the number of times the word \"at\" was found in the original string. You may not use any of the string functions (str...). 2. (20 pts) The function int findchar(char c, char s[) searches a string in arrays for the first instance of the character in c. The function returns the index (location) of c in s[] if it finds it, and -1 otherwise. Write a main program to test findchar. Your program should include the test strings, and not read them from a file or the terminal. Your program should print out the results of the testing. Do not write the function itself 3. (20 pts) Find and correct three errors in the following function: (extra }'s are not errors) #include find the fourth letter in a string of at least 4 letters. Then modify the string by changing every instance of that letter to the letter A. Return the number of times that letter was found. \"/ int fun4(char s char c; int count-0 inti c s[4]; for(i-0; s[i]!=\"10\" if (sli]c){ s[i]= A';} } return count; 4. (20 pts) The following program reads in the name of a city and prints it out. Modify it to read in the name of a city and state, separated by a space, and print them out. If it reads Tulsa Oklahoma, it should print: The city is Tulsa, the state is Oklahoma. int getword(char w, int l); #include main) (int len; char city[100]; len getword(word, 100); printf(\"The City is %s\", city); return 0; #include int getword(char word], int limit) int n; char c; for(n-0; (c getchar0)! - EOF) & &(c!=' )&& (n)>