> Please help Chemistry question?

Please help Chemistry question?

Posted at: 2014-06-09 
Blood is buffered by H2CO3/HCO3- buffer system. The concentration of HCO3- in blood plasma is 0.024 M and that of H2CO3 is 1.2*10^-3M. The pKa of Carbonic acid at the body temperature is 6.1. What is the ratio of HCO3-/H2CO3 in blood plasma? What is the pH of blood plasma?