The Henry’s law constant of CO$_2$ is $3.4 \times 10^{-2}$ M/atm at 25$^\circ$C.
Dissolved CO$_2$ undergoes:
CO$_2 \cdot$H$_2$O $\rightleftharpoons$ H$^+$ + HCO$_3^-$ ($K_1 = 4.3 \times 10^{-7}$ M)
HCO$_3^- \rightleftharpoons$ H$^+$ + CO$_3^{2-}$ ($K_2 = 4.7 \times 10^{-11}$ M)
If ambient CO$_2$ concentration is 300 ppm, the total dissolved CO$_2$ (in $\mu$M, rounded off to one decimal place) is __________.