a.
The dilation is a reduction, this comes from the fact that the dilation factor is less than 1.
b.
A point after a dilation is given as:
[tex](x,y)\rightarrow(kx,ky)[/tex]where k is the dilation factor.
In this case we need to divide all the coordinates by two, then we have that:
[tex]\begin{gathered} P^{\prime}(-\frac{5}{2},\frac{1}{2}) \\ Q^{\prime}(-1,3) \\ R^{\prime}(\frac{3}{2},\frac{7}{2}) \\ S^{\prime}(3,2) \end{gathered}[/tex]