Summarizing
1. Consideration is the benefit which must be agreed between two parties. When the bargain is settled, it brings the tow parties into the contract. One consideration should be exchanged with another consideration, and that is why contracts take place. Both parties should be benefiting somehow from the contract.
2. A mirror image rule means that the offer must be accepted exactly the way it is without any modifications. This is mostly focused on contracts and so whatever the contract states, that is exactly what should be accepted by both parties.
3. 'Joint And Several Liability '
Joint and several liability is when multiple parties can be held liable for the same event or act and be responsible for all restitution required. In cases of joint and several liability, a person who was harmed or wronged by several parties could be awarded damages and collect from any one, several, or all of the liable parties. The liable parties would be required to pay the entire damage award, which could be split among multiple parties or could come from just one party. Each party would be liable for part of the damages, or up to as much as all of the damages.