Unit 4 will be marked out of 100, like Unit 3 was. Both sacs will be marked out of 30 and then scaled to a mark out of 50.
I think the Unit 4 context piece will be a little more difficult than the context sac in Unit 3, mainly because you have to write such a large amount without diverging from your main ideas. In Unit 3 I had to write three context pieces, which was easier because flexibility was large (Expository piece and two Imaginative pieces). I think one massive piece will be quite difficult to top score in. However saying that, if you have an extensive knowledge of the text, you should have enough ideas to meet the required word limit whilst getting your point across to the marker.
I seemed to have forgotten the boundaries of a text response haha. I'm writing drafts for U401 and my ideas are way to broad. I will need to find a way to contain my ideas into relative textual evidence, rather than a philosophical stance on the concept of chance. I think that because most of Unit 3 (well for me anyway) was based around Expository, Creative and LangAn, text-responses have been in the back of most of my cohorts heads. But i'm sure in the next week I can get my head back around it all. It's starting to kick back in after I wrote another essay tonight.
Best of luck for U4!