Can someone please explain this step by step?

The Oberth effect says that we can accomplish certain maneuvers more cheaply if we apply the thrust when we are already traveling fast. Compute $$vbc for the combination of maneuvers $($b$)$ and $($c$)$: that is$,$ how much $$v do you need to apply from low Earth orbit to escape from Earth and have enough excess speed to accomplish maneuver $($b$)?$ Do the same for $$vde$,$ which is just the reverse process occuring at Mars. Compute the revised total mission $$v$.$