The diagonal of a square is 10√2 units. Find the length of its sides and its perimeter.
a) Side length: 5 units, Perimeter: 20 units
b) Side length: 10 units, Perimeter: 40 units
c) Side length: 10√2 units, Perimeter: 40√2 units
d) Side length: 5√2 units, Perimeter: 20√2 units