An isotope is radioactive . It is being produced at constant rate b . Half - life of radioactive substance is a . After some time no.of radioactive nuclei become constant . Then value of this constant is .

Question

$(a)\;ln 2\qquad(b)\;ab\qquad(c)\;\large\frac{ab}{ln 2}\qquad(d)\;\large\frac{a}{b}$