need help with this program in PYTHON:

for the file, make up a plain.txt file with any words in it

Write a function that reads the contents of a text file. The function should create a dictionary in which the keys are the individual words from the file, and the values are the number of times each word appears in the file. The main program should ask the user for the name of the file to read, pass that name to the function, and get the dictionary returned from the function. Main should display the word / frequency pairs in alphabetical order one per line. Also display the most frequently used word and the number of times it was used.