[Solved] I don’t understand this Javascript?

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var x = 6; 
var y = 4; 
var a = function(b) {
    return function(c) {
        return y + b + c;
    }
};
x = 2; 
y = 5; // unnecessary, meant to confuse
var fn = a(x); // creates a closure, where b equals 2
x = 1; // unnecessary, meant to confuse
y = 3; 
var unknown = 5;
console.log(fn(unknown)); // y=3,b=2,c=5, total = 10

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solved I don’t understand this Javascript?