A non-engineer tinkers with Simulink

Simulink documentation is short on examples that are (a) simple and (b) do not come from the engineering domain. We present one that meets both criteria and so may aid another non-engineer curious about Simulink.
The models presented in this submission are motivated by a topical, if hardly important :), question.

Chartered Financial Analyst (CFA) is an esteemed professional certification in the field of finance. The CFA program includes three examinations, or levels; to qualify for the CFA charter, a candidate must complete Levels I-III, one examination per year, possibly skipping years and retaking failed examinations.

A CFA charterholder may be proud of completing the program on first attempt, i.e. without retaking any examination. What is the actual weight of such an accomplishment, as suggested by the fraction of CFA charterholders with a 'first-time pass' (FTP)? The statistic is not reported, and relevant data is limited to pass rates for Levels I-III: 40, 40 and 50 per cent respectively, taken to be constant through time.

We focus on drop-out behavior of candidates as the parameter of interest: intuitively, if everyone who fails an examination abandons the program, any charterholder must be an FTP, whereas hordes of repeat test takers ought to make a first-time pass rare.

We make several additional assumptions, notably, that (a) candidates taking an examination for the first time and those retaking it have the same chances of passing and dropping out if failed; (b) a candidate failing an exam re-takes it at first opportunity, i.e. next year; (c) the drop-out rate is constant for Levels I-III. (We may fix it at 50%, for example).

Please make a guess, and proceed to the files. Do let me know if you spot an error, or scope for better design!