Properties and Indexers - General Questions

What is the output of the following program?

var a = new Acc();
a.Balance = -50;
Console.WriteLine(a.Balance);
class Acc
{
    private int bal;
    public int Balance { get => bal; set { if (value >= 0) bal = value; } }
}

What is the output of the following program?

var t = new Temp(); t.F = 212; Console.WriteLine(t.F);
class Temp {
    private double c;
    public double F { get => c * 9 / 5 + 32; set => c = (value - 32) * 5 / 9; }
}

Can properties be declared in interfaces?

A property with only a get accessor is:

What does an init accessor (C# 9) allow?