Write a function t_charcount that takes a string tree as input and counts the total number of characters that the values contain. This is the function's type:

t_charcount : string tree -> int

Example: t_charcount t3 gives 11.

write a function t_concat that will concatenate together the values of a string tree. The function's type is here:

t_concat : string tree -> string

(program in ocaml)