ocaml language code pls

Write a function countc : string -> char -> int such that countc sc counts the number of times character c appears in the string s. So for example counto "acab" 'a' should evaluate to 2; countc "birdofprey" 'z' should evaluate to 0; and countc "zzzzz" 'z' should evaluate to 5. Hint: you will probably find it useful to define a helper function that counts the number of times c appears between either the beginning of the string and a given index or the end of the string and a given index. Write a function right justify : int -> int -> string such that rightjustify w n returns a string representation of n padded with enough spaces in front so that the string has width w. (If the string representation of n has length greater than w, no padding should be added). So rightjustify 5 123 should evaluate to the string 123" and rightjustify 1 314 should evaluate to the string "314