Word has just come from the higher-ups, and you're in charge of building out a domain that keeps track of weightlifters and the gyms they lift at. Yes gyms. Everyone knows you need a weekday gym and a weekend gym. And one for when you're traveling, and one that you go to just to show off. Oh, and that one with a really great steam room. Gotta love the steam room.

Here's what we need to be able to do.

Lifter

• Get a list of all lifters

• Get a list of all the memberships that a specific lifter has

• Get a list of all the gyms that a specific lifter has memberships to

• Get the average lift total of all lifters

• Get the total cost of a specific lifter's gym memberships

• Given a gym and a membership cost, sign a specific lifter up for a new gym

Membership

• Get a list of all memberships

Gym

• Get a list of all gyms

• Get a list of all memberships at a specific gym

• Get a list of all the lifters that have a membership to a specific gym

• Get a list of the names of all lifters that have a membership to that gym

• Get the combined lift_total of every lifter has a membership to that gym