Consider the following class descriptions and code. Account is an abstract class with one abstract method named getInterestRate. BasicCheckingAccount is a concrete class that extends Account. EnhancedCheckingAccount extends BasicCheckingAccount and overrides getInterestRate.

Account acct;
double rate1, rate2;
acct = new BasicCheckingAccount(< parameters not shown >);
rate1 = acct.getInterestRate(); // assignment 1
acct = new EnhancedCheckingAccount(< parameters not shown >);
rate2 = acct.getInterestRate(); // assignment 2

The reference to getInterestRate in assignment 2 is to the class

a. Account

b. EnhancedCheckingAccount

c. SavingsAccount

d. The code cannot run, because the variable acct cannot be assigned to an EnhancedCheckingAccount object in the line before assignment 2.