Solution:''The fine qualities of cotton and silk produced in India had a big market in Europe.... The competition among the European companies inevitably pushed up the prices at which these goods could be purchase(d)"''....By the end of the nineteenth century, half the imports and exports of India passed through Bombay. One important item of this trade was opium that the East India Company exported to Chin(a)"
"Indigo and saltpetre were the other major imports from India, and the fact that both products were produced in the eastern Gangetic plain, especially in Bihar, stimulated British efforts to establish factories on the east coast as well as the west coast of the Indian subcontinent."
So Saltpetre was indeed exported otherwise British wouldn't have made efforts to setup factories on East coast.