How Low Could the Renewal Rate Really Be?

Tunely, a music-streaming app, has $250{,}000$ subscribers. The research team wants to know what share of them will renew next month.

Asking all $250{,}000$ is out of the question, so the team emails a one-question survey — "Will you renew next month?" — to a random sample of $4{,}000$ subscribers. Here is what happened:

• 12% of the $4{,}000$ emails bounced and were never delivered.
• Of the emails that were delivered, 45% were answered.
• Of the subscribers who answered, 75% said they would renew.

The team reports 75% as its estimate for all $250{,}000$ subscribers.

A reviewer refuses to accept that number and asks for the worst case instead. Her assumption: every subscriber in the original $4{,}000$-person sample who did not answer — including every subscriber whose email bounced — would have said no.

Under the reviewer's assumption, what is the lowest possible percentage of the $4{,}000$ sampled subscribers who would renew?

Give your answer as a percentage (a number between 0 and 100), rounded to 2 decimal places.