A sample containing 224 88 Ra, which decays by -particle emission, disintegrates at the following rate, expressed

A sample containing ²²⁴₈₈Ra, which decays by α-particle emission, disintegrates at the following rate, expressed as disintegrations per minute or counts per minute (cpm): t = 0, 1000 cpm; t = 1 h, 992 cpm; t = 10 h, 924 cpm; t = 100 h, 452 cpm; t = 250 h, 138 cpm. What is the half-life of this nuclide?