A 10ft streetlamp stands on level ground. A 6ft tall person is x feet from the base of the lamp and casts a shadow of length s feet along the ground. Which of the following equations correctly relates x and s at that instant?
(a) 10(x+s)=6s
(b) 6(x+s)=10x
(c) 10s=6(x+s)
(d) 10s=6x