If Helena types 52 words in one minute, then she will double that in two minutes, typing 104 words. If she types for four minutes, she types for two minutes, and then another two minutes, which can be written as 104+104, and 104+104=208. Therefore, Helena types 208 words in four minutes.
A combination of supernatural forces, a manipulative wife, three scheming witches and Duncan's decision to announce his son future king are all influencing factors in Macbeth's ultimate decision to murder King Duncan.