Answer
The rate of change for mass is $0.024 kg/s$
Work Step by Step
First we calculate for density
$ρ=(0.02g)/(50mm^3)=4\times10^{-4}g/mm^3=4\times10^{-4}kg/cm^3$
Then we solve for the rate of change for mass using $m=ρAh$
area of container $=(14cm)(17cm)=238cm^2$
$\frac{dm}{dt}=(4\times10^{-4}kg/cm^3)(238cm^2)(0.25 cm/s)=0.024kg/s$
