Answer:
Adding the transition “however” at the beginning to connect the ideas better.
Step-by-step explanation:
"However" is a transition word that is used to connect ideas in the text. In this case the author needs to connect sentence 4 ("Opponents argue that tablets aren’t a good choice because initially they’re very expensive.") to sentence 5 ("The secretary of education pointed out that tablets can be updated regularly, which saves money in the long run.") In other words, he tries to connect an idea of those that are against the use of tablets in schools to an argument in favor of it's use. To introduce a statement that constrasts with something that was said before "however" is used.
We can't replace "money" with "dough" as it is an informal way to name money, we are trying to convince audience giving arguments, formal words are needed. The same thing happens with the phrase "are awesomely fast" it takes away seriousness.