function [ub, uu, x]=u_ivp(lambda, a, b, ua, reltol, abstol, Npts)

IVs = [ua; 1];
opt = odeset('RelTol',reltol,'AbsTol',abstol);

[x u] = ode45(@rhs, linspace(a,b,Npts), IVs, opt, lambda);

%  u(b) and u(x)
ub = u(end,1);
uu = u(:,1); 
