If a fair coin (a coin which shows heads or tails with equal probabilities when tossed) shows heads upon tossing, 4 numbers are selected from 1, 2, 3, ... 100 (a number once selected is not selected again) and if tails shows up, 3 numbers are drawn from 3, 6, 9, 12, ... 99 (a number once selected is not selected again). Determine the probability of the event that the sum of the selected numbers is even.

2)

Iron deficiency is known to exist in 28%, 14% and 5% of the people of three different tribes T1, T2 and T3 respectively. All the three tribes have equal population. An investigator selects a person from one of the tribes randomly, from the total population of the three tribes and examines for iron deficiency. It turns out that the selected person does not have the deficiency. Determine the probability that this person belonged to tribe (i) T1, (ii) T2, (iii) T3.