Use the right-endpoint approximation to approximate the area under the curve of $f(x)=1-\frac{x}{5}$ on the interval $[-2,4]$ using $n=3$ rectangles. Submit your answer using an exact value. For instance, if your answer is $\frac{10}{3}$, then enter this fraction as your answer in the response box. Provide your answer below:

Step 1 ：Define the function \(f(x)=1-\frac{x}{5}\) and the interval \([-2,4]\).

Step 2 ：Divide the interval into \(n=3\) equal subintervals, each of width \(2\).

Step 3 ：Determine the right endpoints of these subintervals, which are \(0, 2, 4\).

Step 4 ：Calculate the height of each rectangle by evaluating the function at these right endpoints, which gives \(f(0)=1, f(2)=0.6, f(4)=0.2\).

Step 5 ：Calculate the area of each rectangle by multiplying its width by its height, which gives \(2*1=2, 2*0.6=1.2, 2*0.2=0.4\).

Step 6 ：Sum the areas of these rectangles to approximate the total area under the curve, which gives \(2+1.2+0.4=3.6\).

Step 7 ：The total area under the curve of the function \(f(x)=1-\frac{x}{5}\) on the interval \([-2,4]\) using the right-endpoint approximation with \(n=3\) rectangles is approximately \(\boxed{3.6}\).