A 40-L tank initially contains 10 g of salt. Brine whose concentration varies with time according to (1+0.1t) g/L flows into the tank at 4 L/min, and the mixture leaves at the same rate so that the volume remains constant. What is the amount of salt in the tank after 5 minutes?
a) 30.0 g
b) 24.0 g
c) 26.1 g
d) 32.4 g