The formula for calculating simple interest is \(I = Prt\), where \(I\) is the interest, \(P\) is the principal, \(r\) is the interest rate per annum, and \(t\) is the time in years. In this case, we have \(I = \$4890\), \(P = \$8550\), and \(t = 3\). Substituting these values into the formula, we get:

\(\$4890 = \$8550 \times r \times 3\)

Solving for \(r\), we get:

\(r = \frac{\$4890}{\$8550 \times 3} \approx 0.19047619047619047\)

Multiplying by 100 to convert to a percentage, we get:

\(r \approx 19\%\)