A mineral deposit along a strip of length 7 cm has density s(x)=0.04x(7−x) g/cm for 0≤x≤7. Calculate the total mass of the deposit.

Answer 1

I guess you want
∫[0,7] s(x) dx = ∫[0,7] 0.04x(7-x) dx = 2.28667 g