A book contains 40000 words. For each word, the probability that it is printed wrongly is 0.0001 and these errors occur independently. The number of words printed wrongly in the book is represented by the random variable $X$.

a) State the exact distribution of $X$, including the values of any parameters.

b) State an approximate distribution for $X$, including the values of any parameters, and explain why this approximate distribution is appropriate.

c) Use this approximate distribution to find the probability that there are more than 3 words printed wrongly in the book.