Assignment task: John's shoulders and hips are not aligned. His eyes are not level with the top of the screen. The chair is too low and his feet are not flat on the floor. His elbows aren't by his side which means his wrist isn't in the correct position.
First, he should adjust his chair so that his feet are flat on the floor. He should sit up straight and bring the laptop closer to him to adjust his elbows and wrists.
Three long-term consequences could be tendinitis and/or carpal tunnel syndrome, static loading, and mechanical contact stress.