The electrons, identified by quantum numbers n and l, (i) n = 4, l = 1, (ii) n = 4, l = 0,  (iii) n = 3, l = 2, and (iv) n = 3, l = 1 can be placed in order of increasing energy, from the lowest to highest, as

The two guiding rules to arrange the various orbitals in the increasing energy are :(i) Energy of an orbital increases with increase in the value of n + l.(ii) Of orbitals having the same value of n + l, the orbital with lower value of n has lower energy.Thus for the given orbitals , we have(i) n + l = 4 + 1 = 5                 (ii) n + l = 4 + 0 = 4(iii) n + l = 3 + 2 = 5                 (iv) n + l = 3 + 1 = 4Hence, the order of increasing energy is(iv) < (ii) < (iii) < (i)