Fall 2015, Q15: UEPR calculation

The question says "On April 1, 2014, the company wrote its first and only insurance policy -- a 12 month WC policy". In this case, I would have proceeded as below.

EP = (9/12) * WP
UEPR = 50% (WP - EP)

The official CAS solution uses 8.5/12 for EP calculation. Should't this apply only if policies were written uniformly through out the whole month? What am I missing?


Fall 2015, Q15: UEPR calculation