1. **Problem 1: Calculate the interest rate $r$ given principal $P=5439$, rate $r=8.5\%$ per annum, and amount $A=X$.** Since the problem states $r=8.5\%$ per annum, this is the interest rate. If $X$ is the amount after interest, then the formula for simple interest is: $$A = P(1 + rt)$$ where $t$ is time in years. However, $t$ is not given, so we cannot find $X$ without $t$. If $t$ is known, substitute values to find $X$. 2. **Problem 2: Given principal $P=10450$, amount $A=10600$, find the interest rate $r$.** Using the simple interest formula: $$A = P(1 + rt)$$ Assuming $t=1$ year (since not specified), solve for $r$: $$10600 = 10450(1 + r \times 1)$$ Divide both sides by 10450: $$\frac{10600}{10450} = 1 + r$$ Calculate the left side: $$1.01435 = 1 + r$$ Subtract 1: $$r = 0.01435$$ Convert to percentage: $$r = 1.435\%$$ **Final answers:** - Problem 1: Interest rate $r=8.5\%$ per annum (time $t$ needed to find amount $X$). - Problem 2: Interest rate $r=1.435\%$ per annum assuming $t=1$ year.