Calculate the equivalent interest rate $\left(r_{2}\right)$ of the following investment: \[ \begin{array}{l} r 1=8.25 \% \\ m_{1}=c a \\ r_{2}=? \\ m_{2}=\mathrm{cm} \end{array} \]

Step 1 ：Given the initial interest rate (r1) as 8.25% and the initial investment amount (m1) as ca. The final investment amount (m2) is given as cm. We are asked to find the final interest rate (r2).

Step 2 ：The formula to calculate the equivalent interest rate is: \(r_{2} = ((m_{2}/m_{1})^{1/n} - 1) * 100\)

Step 3 ：Substitute the given values into the formula: \(r_{2} = ((cm/ca)^{1/n} - 1) * 100\)

Step 4 ：Since we don't have the values of c, a, m, and n, we can't calculate a numerical value for r2. But we can express r2 in terms of these variables using the formula above.

Step 5 ：Final Answer: \(\boxed{r_{2} = 100*(a*m/c)^{1/n} - 100}\)