How to solve

$4\mathrm{.}74$ A first step toward identifying spam is to create a list of words that are more

likely to appear in spam than in normal messages. For instance, there are words

like buy or the brand name of an enhancement drug that are more likely to occur

in spam messages than in normal messages.

A list is available, among the $1000$ messages, the $350$ spam messages have $310$

that contain words on this list and the $650$ normal messages have $70$ that contain

words on the list.

Obtain the probability that a spam message gets through the filter to user's inbox.

Please enter answer as a decimal, eg $0\mathrm{.}1234$