We first form the sequence of visit using (iv), (v) and (vi).
From (iv), we know that Q visits first and U visits last.
From (v), we know that W visits first after break and is followed by R.
From (vi), we know that P visits after break.
Thus, the sequence of visit after break becomes W R P U.
Also, S has the same position in morning session as P in afternoon session. So, sequence of visit before break is Q, T / V, S, V / T.
Clearly, as mentioned, lunch break will be over and doctor W will visit at 1.45 p.m., doctor R will visit at 2.30 p.m., doctor P will visit at 3.15 p.m. and U will visit at 4 p.m.