2019 AP® COMPUTER SCIENCE A FREE-RESPONSE QUESTIONS 1. The APCalendar class contains methods used to calculate information about a calendar. You will write two methods of the class. public class APCalendar { /** Returns true if year is a leap year and false otherwise. */ private static boolean isLeapYear(int year) { /* implementation not shown */ } /** Returns the number of leap years between year1 and year2, inclusive. * Precondition: 0 <= year1 <= year2 */ public static int numberOfLeapYears(int year1, int year2) { /* to be implemented in part (a) */ } /** Returns the value representing the day of the week for the first day of year, * where 0 denotes Sunday, 1 denotes Monday, ..., and 6 denotes Saturday. */ private static int firstDayOfYear(int year) { /* implementation not shown */ } /** Returns n, where month, day, and year specify the nth day of the year. * Returns 1 for January 1 (month = 1, day = 1) of any year. * Precondition: The date represented by month, day, year is a valid date. */ private static int dayOfYear(int month, int day, int year) { /* implementation not shown */ } /** Returns the value representing the day of the week for the given date * (month, day, year), where 0 denotes Sunday, 1 denotes Monday, ..., * and 6 denotes Saturday. * Precondition: The date represented by month, day, year is a valid date. */ public static int dayOfWeek(int month, int day, int year) { /* to be implemented in part (b) */ } // There may be instance variables, constructors, and other methods not shown. }   (a) Write the static method numberOfLeapYears, which returns the number of leap years between year1 and year2, inclusive. In order to calculate this value, a helper method is provided for you. • isLeapYear(year) returns true if year is a leap year and false otherwise. Complete method numberOfLeapYears below. You must use isLeapYear appropriately to receive full credit. /** Returns the number of leap years between year1 and year2, inclusive. * Precondition: 0 <= year1 <= year2 */ public static int numberOfLeapYears(int year1, int year