Write the necessary code between that calculates user grades. The script should display (alert) the message as follows: 1. If the input is empty, then "Calculate button should display a message "The input is empty - Grades cannot be calculated". 11. If the input is a -ve number, then Calculate button should display a message "The input is -ve - Grades cannot be calculated". m. If the input is >=0 and = 50 and |-hl> Calculate Grades |p>Please type marks between 0 and 100