Question

what type of event must happen for the exchange rate to change from R8:$1 to R9:$1 and the amount of usd traded daily to increase?

Answer 1

If the excange rate from R8:$1 becomes R9:1$ that means that the currency devalueted, and as we've been told that the amount of usd traded daily increased, that leads to logical answer - the central bank of a country had been buying the currency(usd).