(1 point) Consider the Boundary-Initial Value problem 22 и 9 მე2 = a² u 0<x<4, t>0 Ət² u(0,t) = 0, u(4,t) = 0, t>0 ди u(x, 0) = x(4-x), (x, 0) = 0, 0 < x < 4 Ət This models the displacement u(x,t) of a freely vibrating string, with fixed ends, initial profile x (4 - x), and zero initial velocity. The solution u(x,t), is given by the series u(x,t) where bn and Cn = = 4 n=1 ㅠ sin (n = 7 x) cos(cnt) bn sin n