Error in prob­lem 8.4 & remark in prob­lem 11.1

Dear par­ti­cipants!

The Com­mit­tee of the Olympi­ad apo­lo­gises for an error in prob­lem 4 for R8. There should be 20 kJ sup­plied instead of 32 kJ.

Also the remark was added for the prob­lem 11.1 to cla­ri­fy the aver­age speed.