SAT course statistics and question pool

I think that there would a couple things that would vastly improve the quality of the SAT course on Khan Academy:

- A timer showing how long you took for a question after it has been completed

- average amount of questions correct per category

- average amount of questions correct in total

- Randomized question types based on how often they show up on the SAT (if linear equations are 1/8th of the test, the randomized question queue should give me questions about linear equations 1/8th of the time