In the envelope you should find some plain A4 paper.
Also attached are instructions how to make a sonobe cube. Use this paper to make 10 of these cubes. If you have trouble making the cubes, type sonobe cube into YouTube and click on the first result. This will make it a little clearer.
Once you have made 10 of them, leave 5 of them in bus stops, and 5 on benches around Norwich city centre (anywhere within the specified radius shown on the attached map) on Saturday the 18th of February. Take an image of the cubes in each location.
On Sunday the 19th, go back to each location. If any of the cubes are still there, take them home with you and unfold them.
Get the images developed to standard 4×6 size and mount each photograph on its own piece of A4 black card and keep any unfolded cubes with the appropriate photograph. (If any of them remain there at all).
I will reimburse you for the image printing on the day.