paragraph max-width?

Trying to set paragraphs to have max-width 40em..

I even tried:

.p {
max-width: 40em!important
}

in additional-css – but it seems to get overriden by:
.entry-content[ast-blocks-layout] > * {

So, wondering how to get paragraphs to be not so wide (and centered margin-auto if they are not taking up an entire block)

Any ideas? thanks!
Steve

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