# The gravitational field due to mass distribution is $E= k/x^3$ in the x direction where k is a constant. Taking gravitational potential to be zero at infinity, its value at a distance x is
$(a)\;\frac{k}{x} \quad (b)\;\frac{k}{2x} \quad (c)\;\frac{k}{x^2}\quad (d)\;\frac{k}{2x^2}$