Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Series\nnumber | Key | Composed | Published | Opus No. | Brown | Kobylańska | Chominski | Dedication | Notes |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| – | G, B♭ | 1826 | 1826 | – | B. 16 | KK IIa/2-3 | S 1/2 |  | Revised versions (original versions were published in 1875) |
| 1–4 | F♯m, C♯m, E, E♭m | 1830 | 1832 | Op. 6 | B. 60 |  | C. 51–54 | Countess Pauline Plater |  |
| 5–9 | B♭, Am, Fm, A♭m, C | 1830–31 | 1832 | Op. 7 | B. 61 |  | C. 55–59 | M. Johns de la Nouvelle-Orléans | Nos. 2 and 4 are revised versions; the original version of No. 4 was published in 1902 |
| 10–13 | B♭, Em, A♭, Am | 1832–33 | 1834 | Op. 17 | B. 77 |  | C. 60–63 | Mlle. Lina Freppa |  |
| 14–17 | Gm, C, A♭, B♭m | 1834–35 | 1836 | Op. 24 | B. 89 |  | C. 64–67 | Comte de Perthuis |  |
| 18–21 | Cm, Bm, D♭, C♯m | 1836–37 | 1837 | Op. 30 | B. 105 |  | C. 65–71 | Princess Maria Czartoryska de Württemburg |  |
| 22–25 | G♯m, D, C, Bm | 1837–38 | 1838 | Op. 33 | B. 115 |  | C. 72–75 | Countess Roza Mostowska |  |
| 27 | Em | 1838 (28 November) | 1840 | Op. 41/2 | B. 122 |  | C. 77 |  |  |
| 26,\n28–29 | C♯m, B, A♭ | 1839 (July) | 1840 | Op. 41/1, 3–4 | B. 126 |  | C. 76, 78–79 | Étienne Witwicki |  |
| 50 | Am | 1840 (summer) | 1841 | – | B. 134 | KK IIb/4 | S 2/4 |  | Notre temps; in "Six Morceaux de salon" |
| 51 | Am | 1840 | 1841 | – | B. 140 | KK IIb/5 | S 2/5 | Émile Gaillard | In "Album de pianistes polonais" |
| 30–32 | G, A♭, C♯m | 1841–42 | 1842 | Op. 50 | B. 145 |  | C. 80–82 | Leon Szmitkowski |  |
| 33–35 | B, C, Cm | 1843 | 1844 | Op. 56 | B. 153 |  | C. 83–85 | Catherine Maberly |  |
| 36–38 | Am, A♭, F♯m | 1845 (June–July) | 1846 | Op. 59 | B. 157 |  | C. 86–88 |  |  |
| 39–41 | B, Fm, C♯m | 1846 (early autumn) | 1847 | Op. 63 | B. 162 |  | C. 89–91 | Countess Laura Czosnowska |  |
| 42, 44 | G, C | 1835 | 1855 | Op. posth. 67/1, 3 | B. 93 |  | C. 92, 94 | Anna Mlokosiewicz |  |
| 45 | Am | 1846 | 1855 | Op. posth. 67/4 | B. 163 |  | C. 95 |  |  |
| 43 | Gm | 1849 (summer) | 1855 | Op. posth. 67/2 | B. 167 |  | C. 93 |  |  |
| 47 | Am | 1827 | 1855 | Op. posth. 68/2 | B. 18 |  | C. 97 |  |  |
| 48 | F | 1829 | 1855 | Op. posth. 68/3 | B. 34 |  | C. 98 |  | Quotes the folk tune "Oj, Magdalino" |
| 46 | C | 1829 | 1855 | Op. posth. 68/1 | B. 38 |  | C. 96 |  |  |
| 49 | Fm | 1849 (summer) | 1855 | Op. posth. 68/4 | B. 168 |  | C. 99 |  | "Chopin's last composition"; first published in an incomplete form 1855 |
| – | C | 1833 | 1870 | – | B. 82 | KK IVb/3 | P 2/3 |  |  |
| – | D | 1829 | 1875 | – | B. 31 | KK IVa/7 | P 1/7 |  | Heavily revised 1832 (see B. 71, KK IVb/2; rev. vers. pub. 1880) |
| – | D | 1832 | 1880 | – | B. 71 | KK IVb/2 | P 1/7 |  | A heavily revised version of B.31, KK IVa/7 |
| – | B♭ | 1832 (24 June) | 1909 | – | B. 73 | KK IVb/1 | P 2/1 | Alexandrine Wolowska |  |
| – | D | 1820 (?) | 1910 (20 February) | – | B. 4 | KK Anh. Ia/1 | A 1/1 |  | "Mazurek"; doubtful |
| – | A♭ | 1834 (July) | 1930 | – | B. 85 | KK IVb/4 |  |  |  |
| – | ? | "early" | – | – | – | KK Vf |  |  | "Several mazurkas"; lost |
| – | D | 1826 (?) | – | – | – | KK Ve/5 |  |  | Mentioned in literature; MS unknown |
| – | G | 1829 (22 August) | ? | – | – | – |  |  | Setting of a poem by Ignac Maciejowski |
| – | ? | 1832 | – | – |  | KK Vc/2 |  |  | Mentioned in a letter from Chopin dated 10 September 1832 |
| – | ? | 1832 (14 September) | – | – |  | KK Ve/7 |  |  | Listed in an auction catalogue, Paris, 1906 |
| – | B♭ | 1835 | – | – |  | KK Ve/4 |  |  | MS sold in Paris, 20 June 1977 |
| – | ? | 1846 (by December) | – | – | – | KK Vc/4 |  |  | Mentioned in a letter from Chopin |
| – | A, Dm | ? | – | – | – | KK VIIb/7-8 |  |  | Allegretto and Mazurka; MS sold Paris 21 November 1974 |
| – | B♭m | ? | – | – | – | KK Anh. Ib |  |  | Doubtful |
| – | ? | ? | – | – | – | KK Ve/8 |  |  | Mentioned in 1878 correspondence between Breitkopf & Hartel and Izabela Barczinska |
| – | ? | ? | – | – | – | KK Ve/6 |  | Mme Nicolai | Mentioned in a note from Augener to C.A. Spina 21 May 1884 |
Question:
which is older, 10-13 or 18-21?
Answer:
10-13