A well-stirred 50-L tank initially holds 30 g of salt. Brine containing 2 g/L of salt enters at 5 L/min, and the mixture leaves at the same rate. Approximately what is the salt concentration in the tank after 10 minutes?
a) 2.50 g/L
b) 2.00 g/L
c) 1.48 g/L
d) 0.60 g/L