Final answer:
To minimize the material used, we need to minimize the surface area of the rectangular box. Calculus can be used to find the length (y) that minimizes the surface area given a fixed volume, but the question provides options to determine which one leads to the least material used.
Step-by-step explanation:
To find the length (y) that would minimize the amount of material used for the construction of a rectangular box with no top and a volume of 4 cubic inches, we must consider the surface area of the box. The surface area S of a rectangular box with length x, width y, and height h, and without a top is given by S = xy + 2xh + 2yh. Given that the volume V is xyh, and V is 4 cubic inches, we have the equation xyh = 4. This can be rearranged to h = 4/(xy). Substituting this into the surface area formula, we get the surface area solely in terms of x and y: S = xy + 2x(4/(xy)) + 2y(4/(xy)). This simplifies to S = xy + 8/x + 8/y. To minimize the surface area, one would take the derivative with respect to y and set it to zero, then solve for y. Without completing full calculus operations here, the question provides options for y, so we can use those choices along with the constraint xyh = 4 to determine which one leads to the least surface area.