The decay constant of radio isotope is `lambda`. If `A_(1) and A_(2)` are its activities at times `t_(1) and t_(2)` respectively, the number of nuclei which have decayed during the time `(t_(1)-t_(2))`

Options

A. `A_(1) - A_(2)`
B. ` (A_(1) - A_(2)) lambda`
C. `lambda (A_(1) - A_(2))`
D. `A_(1) t_(1) - A_(2) t_(2)`

Answer

B