If else statement problem in android studio : I know this is a very silly question. But i am stuck in this and I have no idea how to solve it.

There are some variables with values:

> float total = 74.67 ; 
  String grade = "", point = "";

And with this values I want to do this:

    if(total>=80){
            grade = "A+";
            point = "4.00";
        }else if(total<=79 && total>=75){
            grade = "A";
            point = "3.75";
        }else if(total>=70 && total<=74) {
            grade = "A-";
            point = "3.50";
        }else if(total<=65 && total>=69){
            grade = "B+";
            point = "3.25";
        }else if(total<=64 && total>=60){
            grade = "B";
            point = "3.00";
        }else if (total<=59 && total>=55){
            grade = "B-";
            point = "2.75";
        }else if (total<=54 && total>=50){
            grade = "C+";
            point = "2.50";
        }else if(total<=49 && total>=45){
            grade = "C";
            point = "2.25";
        }else if (total<=44 && total>=40){
            grade = "D";
            point = "2.00";
        }
        else {
            grade = "F";
            point = "0.00";
        }

but it always shows grade  = "F" and point = "0.00".

if I write this, 

    if(total>=70 && total<=74) {
            grade = "A-";
            point = "3.50";
        }

it shows grade ="" and point ="".
the value of total is showing nicely but there are problem with grade and point. can anyone tell me what is the problem?