James is trying to determine the height of a building, so he uses a street sign as a reference. The street sign is 6 feet tall a
nd casts a shadow of 3 feet. The two triangles formed in the picture above are similar. If the building casts a shadow of 21 feet, what is the height of the building?
A.45 feet
B.42 feet
C.63 feet
D.11 feet
