Can this query be faster?

Hi all,

This query spends 24 seconds to obtain the
result. What can be optimized?
Every time I run this query I only need information
related to 10 'articulos' and then I use 'OFFSET' clause
to search forward or backward.

+-----------------------
Select articulos.codarticulo, articulos.descripcion,
sum(stocks.stkreal) as tot
>From articulos, prendas, stocks
Where articulos.codarticulo = prendas.codarticulo
And prendas.codprenda = stocks.codprenda
Group by articulos.codarticulo, articulos.descripcion
Limit 10;
+-----------------------

Table 'articulos' has 4049 records
Table 'prendas' has 29493 records
Table 'stocks' has 90747 records

cad=# \d articulos
Table "articulos"
Attribute | Type | Modifier
--------------+---------------+-----------------------------
codarticulo | char(20) | not null default '0'
descripcion | varchar(40) | default ' '
refproveedor | char(20) | default ' '
codproveedor | char(5) | not null default ' '
venautoriz | boolean | not null default 't'::bool
comautoriz | boolean | not null default 't'::bool
codtallaje | char(2) | not null default ' '
codtarifa | char(2) | not null default ' '
apldtocli | boolean | not null default 'f'::bool
precompra | numeric(30,6) | not null default 0.1
pretarifa | numeric(30,6) | not null default 0
premedio | numeric(30,6) | not null default 0
precosto | numeric(30,6) | not null default 0
pvpsegun | varchar(15) | not null default 'Indicado'
impuesto | numeric(30,6) | not null default 0
codfamilia | char(5) | not null default ' '
ubicacion | char(10) | not null default ' '
observ | varchar(2048) | not null default ' '
preultcompra | numeric(30,6) | not null default 0
Indices: articulos_pkey,
idxarticulos_codarticulo,
idxarticulos_codfamilia,
idxarticulos_codproveedor,
idxarticulos_descripcion,
idxarticulos_refproveedor

cad=# \d prendas
Table "prendas"
Attribute | Type | Modifier
-------------+----------+---------------------------------------------
codarticulo | char(20) | not null default '0'
codcolor | char(3) | not null default '000'
numtalla | char(2) | not null default '00'
codprenda | integer | not null default nextval('codprenda'::text)
Indices: idxprendas_codarticulo,
idxprendas_codcolor,
idxprendas_codprenda,
idxprendas_numtalla,
prendas_pkey

cad=# \d stocks
Table "stocks"
Attribute | Type | Modifier
------------+----------+-------------------------
stkreal | integer | not null default 0
stkpterec | integer | not null default 0
stkpteser | integer | not null default 0
stkminimo | integer | not null default 999999
codprenda | integer | not null default 0
codalmacen | char(10) | not null default ' '
Indices: idxstocks_codalmacen,
idxstocks_codprenda,
stocks_pkey

cad=# Explain Select articulos.codarticulo, articulos.descripcion,
sum(stocks.stkreal) as tot
From articulos, prendas, stocks
Where articulos.codarticulo = prendas.codarticulo and
prendas.codprenda = stocks.codprenda
Group by articulos.codarticulo, articulos.descripcion Limit 10;

NOTICE: QUERY PLAN:
Aggregate (cost=485333365.76..493587395.74 rows=110053733 width=48)
-> Group (cost=485333365.76..490836052.41 rows=1100537331 width=48)
-> Sort (cost=485333365.76..485333365.76 rows=1100537331 width=48)
-> Merge Join (cost=310247.47..334885.36 rows=1100537331 width=48)
-> Index Scan using stocks_pkey on stocks (cost=0.00..5233.94
rows=74469 width=8)
-> Sort (cost=310247.47..310247.47 rows=1477846 width=40)
-> Merge Join (cost=648.57..2429.70 rows=1477846 width=40)
-> Index Scan using prendas_pkey on prendas
(cost=0.00..1403.44 rows=24077 width=16)
-> Sort (cost=648.57..648.57 rows=6138 width=24)
-> Seq Scan on articulos (cost=0.00..262.38 rows=6138
width=24)

EXPLAIN
cad=#