OCAML CODE ONLY. FULL PROGRAM. INCLUDING HELPER FUNCTIONS FOR FILE I/O. USE STRING.CONTAINS. NO ARRAYS.

Write a program with OCaml.

Your program will consist of a function that accepts two strings. Each string is the name of a file. The first is the name of an input file and the second is the name of an output file. Name the function pangram. (Note that your program can also make use of other helper functions. Just make sure the function pangram takes as argument a pair of string describing the input file and output file.)

A pangram is a sentence that contains all the letters of the English alphabet at least once. For example, the following sentence:

the quick brown fox jumps over the lazy dog 

is a pangram. The program you are to write must read in an input file (input.txt, a plain text file which contains some sentences, one on each line), line by line and check if the line read is a pangram or not. If the sentence read is a pangram, it writes true to the output file. If it is not, it writes false to the output file.