Given that: AD = 8 cm, AJ = 6 cm, AI = 5 cm, AH = 3 cm, AG = 2.5 cm, and FG, BH, EI, and CN are perpendicular on diagonal AD from the vertices F, V, E, and C respectively, what is the length of the diagonal AC?
a) 13 cm
b) 14 cm
c) 15 cm
d) 16 cm