help please

1. What is the difference between an object and a class? Give some examples. 2. Explain the difference between a programmer-defined exception that extends the Java Exception class and one that extends the Java RunTimeException class. 3. The method Sum listed below returns the sum of the integers between 1 and n. What is the order of Magnitude Big O for the Sum function? public int Sum (int n) // Precondition: n is > 0 int total = 0; for (int i = 1; i