Three halogenoalkanes' K,L and M of general formula RCH₂X (where X is CL, Br or I) are heated at 60°C with aqueous silver nitrate solution.

K forms a yellow precipitate, M forms a white precipitate but the colour of the precipitate formed by L might be cream or it might be pale yellow, it is hard to tell
a: Give the formula of the precipitates formed by K and M
b: Explain how the precipitate are formed
c: Describe a test which be carried out on the precipitate formed from L which would halogen was present in L