C3 Volume of Revolution

I've been able to do all the other questions with easy, simply using the two formulas - when it's rotated about the x-axis, the limits of the integral are given as the lines x=a and x=b. Similarly, when it's rotated about the y-axis the limits are y=c and y=d...

However in part b) for both question 8 and 9, the curves are being rotated about the x-axis yet the line y=k is also specified. How am I meant to go about this?

Thanks.

TLDR question 8)b) and 9)b) are different from all the rest. Help please!

Let's do 9b:

Integrate y^2=x+4 between x=0 and x=5.

Now integrate the square of y=(3/5)x between the same values - so you would be integrating (9/25)x^2 between x=0 and x=5.

Now take this volume and subtract it from the volume of PQ...

So Volume(PQ) - Volume(y=3x/5) = Volume of region R.