From I, we conclude that the girl is either Kunal's or his brother's wife. But, according to II, Kunal has no siblings.
So, from both I and II, we conclude that the girl is Kunal's wife.
From III, we find that the girl is the only daughter-in-law of Kunal's mother i.e. she is Kunal's wife.
From I, we have: P > D, P > N, T > P i.e. T > P > D > N or T > P > N > D ...(i)
From II, we have: R > Q, T > R i.e. T > R > Q ...(ii)
From III, we have: T > Q, R > Q ...(iii)
Clearly, from (i) and (ii), we conclude that T is taller than each one of P, N, D, R and Q. So, T is the tallest.
From III, we have: Rajan's basic salary = Rs. 1550.
From I, we have: Vasu's basic salary = Rs. (1550 + 100) = Rs. 1650.
From II, we have: Rajan's other allowances = Rs. 2000 and Vasu's other allowances = Rs. 2050.
Therefore Vasu's monthly salary = Rs. (1650 + 2050) = Rs. 3700.
From I and II, we conclude that Mathematics period began at 9.00 a.m., Biology period began at 8.00 a.m. and Physics period began at 11 a.m. So, the Chemistry period began at 10.00 a.m.
From I and III, we conclude that Mathematics period ended and Chemistry period began at 10.00 a.m.
From the given statement, the descending order of heights is :__, Q,__, S,__.
From II, we have the order: _, Q, R, S,__. Thus, R is in the middle.
From III, we have the order : P, Q,__, S,__. But, according to I, T is not the shortest.
So, R is the shortest. Thus, we have the order : P, Q, T, S, R. So, T is in the middle.
From I, we have: M > V, V > S, V > N ...(i)
From II, we have: Mukul is the oldest ...(ii)
From III, we have: S > N ...(iii)
Combining (i) and (iii), we get :M > V, V >S > N or M>V > S > N. Clearly, Nikunj is the youngest.
From II, we know that Copal's brother was born in 1982.
From III, we find that Gopal's brother was 8 years younger to him i.e. Gopal was born in 1974.
From I, we find that Sanjay is 6 years older than Gopal. Thus, Sanjay was born in 1968.
Observing I, II and III, we find that similar letters have similar code symbols at the corresponding places in the code. So, this is direct-coding.
Thus, to find the code for DATE, we need the code for D which can be obtained from I only (i.e. $.) and the codes for A, T and E which can be obtained either from II or III (@, # and % respectively).