Help me get my bike repaired!

Hi. My bicycle is my only form of transportation (I can't afford a car or public transit). I use it for commuting, I take the cats to the vet when they need, and do all my grocery shopping and errand running with my bike (which is named Alexander). Without a reliable form of transportation, I feel completely immobilized and helpless.

I recently took it in to the shop for repairs, and after riding through the winter, it turned out that it needs a LOT of help. The chainrings, derailleur, basically the whole drivetrain need replaced, the front wheel hub is loose, and i found out today that the brakes need to be completely replaced. Since I have disc brakes, this is going to be expensive.

The original work they told me about was going to cost $240, which includes parts and labor. However, they told me that disc brakes start at $120 (for BB5s), not counting labor. My best bet is to get BB7s, which are guaranteed not to fail and are much easier to maintain, and also have more braking power. These cost $170. I also have labor for the installation to factor in, and I'm not sure what that will cost.

Any money past the $410 for fixing the bike that is raised will be used for bus fare.

Thanks for your support!

-Erica