#### Answer

(a) $A \cdot B = -18$
(b) $A \cdot B = 10$

#### Work Step by Step

We can use the formula for the dot product of two vectors $A$ and $B$:
$A\cdot B = A_x~B_x + A_y~B_y$
(a) $A \cdot B = A_x~B_x + A_y~B_y$
$A \cdot B = (3)(2)+(4)(-6)$
$A \cdot B = -18$
(b) $A \cdot B = A_x~B_x + A_y~B_y$
$A \cdot B = (3)(6)+(-2)(4)$
$A \cdot B = 10$