To solve this problem, we need to use the calibration plot to determine the concentration of Cu2+ ions in the water sample. Since the calibration plot shows a linear relationship between peak current and concentration, we can use the equation of a straight line to find the concentration.The equation of a straight line is y = mx + b, where y is the dependent variable in this case, peak current , x is the independent variable concentration of Cu2+ , m is the slope of the line, and b is the y-intercept.First, we need to find the slope m and the y-intercept b using the given range of concentrations 5-50 M and their corresponding peak currents. To do this, we need at least two points on the calibration plot. However, we are not given specific points, so we cannot determine the exact slope and y-intercept.Assuming we have the slope m and y-intercept b from the calibration plot, we can plug in the peak current 0.25 mA as the dependent variable y and solve for the concentration of Cu2+ ions x .0.25 mA = m * concentration of Cu2+ + bTo find the concentration of Cu2+, rearrange the equation:Concentration of Cu2+ = 0.25 mA - b / mWithout the specific slope and y-intercept values, we cannot provide an exact concentration of Cu2+ ions in the water sample. However, this equation can be used to find the concentration once the slope and y-intercept are determined from the calibration plot.