How to calculate volume of revolution between a curve and a line

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I am currently trying to solve this problem:

The area bounded between $y = x^2$ and $y = 4$ is rotated about the $y$-axis to form a solid. Find the volume generated.

So far, I have only learnt the $\int \pi x^2 dy$ for calculating a solid that is rotated around the y-axis. However, I am having trouble solving this question.

Can someone please help and guide me through on how to solve this problem? Thanks in advance.