Answer: A(20, 10), P(16, 12), R(8, 16), B(0, 20)
R is the midpoint of QS: \(\left(\dfrac{12+4}{2},\dfrac{14+18}{2}\right)=(8,16)\).
Q is the midpoint of PR, so \(P=(2\cdot12-8,\ 2\cdot14-16)=(16,12)\).
P is the midpoint of AQ, so \(A=(2\cdot16-12,\ 2\cdot12-14)=(20,10)\).
S is the midpoint of RB, so \(B=(2\cdot4-8,\ 2\cdot18-16)=(0,20)\).