Mark and his workout partner are lifting weights together, doing many sets of each exercise. On a certain exercise, Mark is using a 40-pound bar, increasing the amount of weight he lifts by 5 pounds on each set. His partner, meanwhile, started out using a 20-pound bar and is upping the weight by adding 10 pounds on every set. Eventually, Mark and his workout partner will be lifting the same amount, and will take turns using the same barbell. How much weight will they be lifting then?