3.

Our best estimate for the true answer is the Richardson extrapolation $$Q_R = (2^2 Q(.05) - Q(.1))/(2^2-1) = 3.4821$$ (since Improved Euler has order p=2). The error being approximately proportional to h², we should have $Q(.01) \approx Q_R + (Q(.1)-Q_R)/100 = 3.4849$.