I'll toss in a configuration similar to what Tim described, although this is probably overkill for what you need. This is the basic configuration for our private cloud accounts. We are provisioning most of our client sites on Digital Ocean. Top notch performance. Super fast SSD drives and solid support.
Load Balancer: 1GB Memory, 1 Core, 30GB SSD Disk, 2TB Transfer ($10/month)
App Server x2: 2GB Memory, 2 Cores, 40GB SSD Disk, 3TB Transfer ($40/month)
DB Server: 4GB Memory, 2 Cores, 60GB SSD Disk, 4TB Transfer ($40/month)
NFS Server: 2GB Memory, 2 Cores, 40GB SSD Disk, 3TB Transfer ($20/month)
You can run this setup for $110 US/Month. Would scale up or down as needed and buy you 45 months of capacity for your 5 grand.
More food for thought
Then again, you could alway try a 8GB, 4 core, 80GB SSD droplet and see what happens. You can use something like LoadStorm to simulate your 100 quiz users.