Julie likens Mark's head to a watermelon
Here's a description of the contestant's attempt. Someone's probably working on collecting some images to illustrate it.
Julie alternates between holding Mark's head and a watermelon, and decides that they are a similar weight. She appears to estimate that his head weighs 3.8kg and that his feet weigh 4kg during her attempt, giving her a total estimate of 7.8kg. This corresponds with what Mark says, in the studio, about her estimate only being about 300g different to Sebastian's, who guessed 7.5kg. She wins the task, since her estimate is closest to the estimate of 9.78kg against which the contestants are being judged.
(Written by Karl Craven)