Two Streptococcus pneumoniae strains, agent 1 and agent 2, are administered to groups of animals at different doses. Mortality rates are then measured for the animals that received each dose level of each agent. Agent 1 is found to have an LD₅₀ of 400. Agent 2 is found to have an LD₅₀ of 600. Which one is producing a capsule and which one is not? How do you know?