2.(15 points) Write a C++ program for the following narrative: A student's letter grade depends upon marks scored by the student. If marks scored are equal to or above 90, then output a message "your grade is A", otherwise if the marks scored are equal to or more than 80, then output a message "your grade is B". If marks scored are equal to or more than 70 then output a message "your grade is C". If the marks are equal to or greater than 60, then output a message"your grade is D". if the marks are less than 60, then output a message " your Grade is F