(9, i) – (10, i- .5) – (11, i); at (11, i) ; at (9, i) ; at (-11, i) ; at (-9, i) ; ]{}

at (-13,8.5) [$r_3$]{}; at (-13,6.5) [$r_2$]{}; at (-13,4.5) [$r_1$]{}; at (-13,-8.5) [$b_3$]{}; at (-13,-6.5) [$b_2$]{}; at (-13,-4.5) [$b_1$]{};

iin [-10,-6,-2,2,6,10]{} [ (i,12) – (i,-12); in [2,...,10]{} [ (i) at (i, ) ; ]{} in [-2,...,-10]{} [ (i) at (i, ) ; ]{} ]{}

iin [-15,...,12]{} at (i, 0) ;

at (-6,-13) [$a$]{}; at (-2,-13) [$b$]{}; at (2,-13) [$c$]{}; at (6,-13) [$d$]{};

=\[draw, fill=black, shape=circle, minimum size=2.5pt,inner sep=0pt\]; (r1) at (-5, 8.5) ; (r1)–(-69); (r1)–(-68);

(r2) at (-3, 8.5) ; (r2)–(-29); (r2)–(-28);

(r3) at (-3, 6.5) ; (r3)–(-27); (r3)–(-26);

(r4) at (-3, 4.5) ; (r4)–(-25); (r4)–(-24);

(r5) at (1, 6.5) ; (r5)–(27); (r5)–(26);

(r6) at (5, 4.5) ; (r6)–(65); (r6)–(64);

(b1) at (-5, -8.5) ; (b1)–(-6-9); (b1)–(-6-8);

(b2) at (-5, -6.5) ; (b2)–(-6-7); (b2)–(-6-6);

(b3) at (-5, -4.5) ; (b3)–(-6-5); (b3)–(-6-4);

(b4) at (3, -8.5) ; (b4)–(2-9); (b4)–(2-8);

(b5) at (3, -6.5) ; (b5)–(2-7); (b5)–(2-6);

(b6) at (3, -4.5) ; (b6)–(2-5); (b6)–(2-4);

(b7) at (5, -8.5) ; (b7)–(6-9); (b7)–(6-8);

(b8) at (5, -6.5) ; (b8)–(6-7); (b8)–(6-6);

(b9) at (5, -4.5) ; (b9)–(6-5); (b9)–(6-4);

=\[draw, shape=circle, 