Two springs with spring constants k1 and k2are put together end-to-end. Let x1 be the amount by which the first spring is stretched relative to its equilibrium length, andsimilarly for x2. If the combined double spring is stretched by anamount b relative to its equilibrium length, then b = x1 + x2. Find the spring constant, K, of the combined spring in terms of k1 andk2.