pona, units of mg/L?

4.2 A mixture of two gas flows is used to calibrate an

air pollution measurement instrument. The calibra-

tion system is shown in Figure 4.23. If the calibration

gas concentration Ceal is 4.90 ppm,, the calibration gas

flow rate Qcal is 0.010 L/min, and the total gas flow

rate Qtotal is 1.000 L/min, what is the concentration

of calibration gas after mixing (Ca)? Assume the con-

centration upstream of the mixing point is zero.