20.
efg
nopqrs

qr
22.
if(PIKACHU.toLowerCase(s.charAt(i)) == 'e')
24.
int count = 0;
for (int i = 0; i < str.length(); i++) {
    if (Character.toLowerCase(str.charAt(i)) >= 'n') {
        count++;
    }
}
System.out.println(count + " letters come after n.");
26. Precondition would be the grades parameter value which is between 0 and 100
28. Its would fail if the a = 0 or if b*b-4ac was negative because there would be no real square root