Solved exercise 6.5.1

Signed-off-by: Rodrigo Dias Ferreira <rodrigodias@gmx.de>
Solved exercise 6.5.2

Signed-off-by: Rodrigo Dias Ferreira <rodrigodias@gmx.de>
Solved exercise 6.5.3

Signed-off-by: Rodrigo Dias Ferreira <rodrigodias@gmx.de>
Solved exercise 6.5.4-6

Signed-off-by: Rodrigo Dias Ferreira <rodrigodias@gmx.de>