Which sum to unity as they should-nbsp find the amount of

Question

Let p denote the probability of some event. Plot the amount of information gained by the occurrence of this event for 0 £ p £ 1.
A source emits one of four possible symbols during each signaling interval. The symbols occur with the probabilities

P₀ = 0.4
P₁ = 0.3
P₂ = 0.2
P₃ = 0.1

which sum to unity as they should. Find the amount of information gained by observing the source emitting each of these symbols.