Answer
(a) $40^{\circ}$
(b) $0^{\circ}$
Work Step by Step
Assume 10 bp per turn in the DNA double helix and poly(A) tract 5 bp long produce a $20^{\circ}$ bend in a DNA strand
(a) If the center base pairs (the third of five) of two successive$(dA)_{5}$ tracts are located 10 bp apart, the bends are additive and the net bend is $40^{\circ}$
(b) If the center base pairs (the third of five) of two successive$(dA)_{5}$ tracts are located 15 bp apart, the bends cancel each other and the net bend is $0^{\circ}$
