The length of a rectangle is 12 cm greater than twice its width. If the perimeter of the rectangle is 48 cm, calculate its length and width.
a) Length: 20 cm, Width: 8 cm
b) Length: 16 cm, Width: 12 cm
c) Length: 24 cm, Width: 6 cm
d) Length: 18 cm, Width: 10 cm