why did we use const &student while overeloading the operator?
Use of const in this video
we did this so that we won’t change the content of the referenced variable . as u know if the function is call by reference then we the changes made to the variable inside the function persists throughout the course of program with const we make sure that this does’nt happen as any attempt to change the value of const variable will result in error
In case of any doubt feel free to ask 
If u got your answer then mark your doubt as resolved