Would you help me with the following question?

An enzyme catalyzes a reaction at a velocity of 20 umol/min when the concentration of substrate (S) is 0.01 M. The Km for this substrate is 1 x 10-5 M. Assuming that Michaelis-Menten kinetics are followed, what will be the reaction velocity when the concentration of S is a) 1 x 10-5 M and b) 1 x 10-6 M.