Read the following passage and solve the questions based on it.
(i) Mr Sharma has five sons—A, K, S, R and N. While going for a party, they wore different coloured shirts viz., Red, Yellow, Blue, White and Green (not necessarily in the same order).
(ii) Each one of them has different likings viz., reading, playing, traveling, singing and writing in no particular order.
(iii) K, who has a liking for singing, does not wear a yellow shirt. S wears a red shirt and does not like reading or writing. N likes to play and does not wear a blue or yellow shirt. A has a liking for writing and R does not wear a yellow or green shirt.
For how many sons can the colour of shirt be definitely determined?