Shapes $A$ and $B$ are similar. a) Calculate the scale factor from shape $A$ to shape B. b) Find the value of $r$. Give each answer as an integer or as a fraction in its simplest form. Not drawn accurately

Step 1 ：First, we need to find the scale factor from shape A to shape B. The scale factor is the ratio of the corresponding sides of the two shapes. In this case, we have \(\frac{6}{4} = \frac{3}{2}\). So the scale factor from shape A to shape B is \(\boxed{\frac{3}{2}}\).

Step 2 ：Now, we need to find the value of r. Since the shapes are similar, the ratio of the corresponding sides is the same. We have \(\frac{r}{6} = \frac{3}{2}\). To solve for r, we can cross-multiply and get \(2r = 18\). Then, we can divide both sides by 2 to get \(r = \boxed{9}\).