A 4.1 g dart is fired into a block of wood with a mass of 20.0 g. The wood block is initially at rest on a 1.6 m tall post. After the collision, the wood block and dart land 3.2 m from the base of the post. Find the initial speed of the dart.

a) 15.4 m/s
b) 18.6 m/s
c) 20.3 m/s
d) 23.1 m/s