Please state whether language L is regular or not. Do only (s), and to prove the answer, use pumping lemma.

L. p) {w: w {a - z}* and the letters of w appear in reverse alphabetical order). For example, spoonfeede q) {w: we {a - z}* every letter in w appears at least twice). For example, unprosperousness EL. r) {w: w is the decimal encoding of a natural number in which the digits appear in a non-decreasing order without leading zeros). s) {w of the form: +, is an element of {0 - 9) and integer is the sum of integer and integers). For example, 124+5-129 L