Let $\mathbf { u } , \mathbf { v } , \text { and } \mathbf { w }$ be vectors. Which of the following make sense, and which do not? Give reasons for your answers. $
a.( \mathbf { u } \times \mathbf { v } ) \cdot \mathbf { w }\quad
b. \mathbf { u } \times ( \mathbf { v } \cdot \mathbf { w } )\ quad
c. \mathbf { u } \times ( \mathbf { v } \times \mathbf { w } )\quad
d. \mathbf { u } \cdot ( \mathbf { v } \cdot \mathbf { w } ).$