Predict the output of the following code snippet:

char ch='B',
char chr=Character.toLowerCase(ch); 
int n=(int)chr-10; 
System.out.println((char)n+"\t"+chr);

Give the output of the following code:

String P = "20", Q ="19";
int a = Integer.parseInt(P);
int b = Integer.valueOf(Q);
System.out.println(a+""+b);

Differentiate between boxing and unboxing.