Does anyone know how to solve these I need help understanding ?

Me with this one question, and i'll upvote the brainliest answer

Find the volume of the described solid. the solid lies between planes perpendicular to the x-axis at x = 0 and x=7. the cross sectionsperpendicular to the x-axis between these planes are squares whose bases run from the parabolay=-31x to the parabola y = 30/x. a) 441b) 147c) 864d) 882

What is the sum of the first 8 terms of the geometric series