How did the British start exporting opium to China ?

(i) When the British conquered Bengal, they made a determined effort to
produce opium in the lands under their control.
(ii) As the market for opium expanded in China, larger volumes of opium
flowed out of Bengal Ports.
(iii) Before 1767 , no more than 500 chests of tea were being exported from
lndia.
(iv) Within four years, the quantity tripled.
(v) A hundred years later, in 1870, the government was exporting about
50,000 chests annually.