(a) Internal trade involves the trade in goods within country while international trade is the type of tad( done between one country and another
(b) Four commodities of internal trade
(i) From the north are
(a) Cattle and
(b) Groundnut
(ii) From the south a
(a) Palm oil and
(b) Kola
(c) Factors that promote trade between Southern and Northern Nigeria are:

(i) Differences in the production of certain goods. Goods produced in the North are different from goods produce in the south, hence the need to exchange goods
(ii) Efficient transportation. e.g road, railway, etc.
(iii) Use of the same currency
(iv) Favourable price attached to the commodities involved in internal trade
(d) Limitations of internal trade:
(i) Long distance between point of production and point of sales
(ii) Language barrier
(iii) High cost of transportation
(iv) Perishability of products.