A wooden piece of great antiquity weights 50 gm and shows C¹⁴ activity of 320 disintegrations per minute. Estimate the length of the time (in years) which has elapsed since this wood was part of a living tree, assuming that living plants show a C¹⁴ activity of 12 disintegrations per minute per gm. The half-life of C¹⁴ is 5730 yrs.  (Round-off to the nearest integer)

$\left[\left(\ln \frac{15}{8}\right)/(\ln 2)=0.907\right]$