Winkleman Associates requires prospective recruits to take an examination that includes both computational and essay questions. It employs contract workers to grade the exams. Hiring of Winkleman recruits takes place four times per year and a different exam is used each time. The contract workers are paid $$25$ per hour to grade the exams.

The last worker to grade exams graded $16$ complete exams. A Winkleman analyst, who is interested in learning curves, estimated that the worker exhibited an $80$ percent learning rate. The worker was paid $$204\mathrm{.}80$ for the last exam $($the $16$th$)$ that was graded.

Required:

Based on the estimated rate of learning, how long did it take the worker to grade the first exam?

What is the percentage of the cost of the $16$th exam to the cost of the $1$st exam?