Write a complete C$++$ program for a pharmacy.

$1-$ The program should store medicine ID and medicine name, number of units available from each medicine, and unit price in a file.

$2-$ The program should have a function that gets medicine ID$,$ medicine name, number of units, and the unit price for all medicine.

$3-$ The program should have a function that displays the number of available units for a given item.

$4-$ The program should have a function that displays the most item sold.

$5-$ The program should have a function that displays the total income for all items sold.

$6-$ The program should have a function that processes any purchase order and update the file.

$7-,$ The user should be able to select the suitable function to be executed when the program starts.