I love it when this happens. When a question I’ve been dreading and have left until last because it looks so monstrously horrible turns out to be really simple. I’d been avoiding the multiple integration questions on this sheet because I have a peculiar blind spot for multiple integrals and find them strangely difficult to do. And then, when all the other questions were done and I could put them off no longer, they turned out to be as easy as falling off a log.