A scientist has a 2.5-gg sample of pure strontium-91, 9138Sr3891Sr. The half-life of strontium-91 is 9.70h.Part (a) Determine its decay constant in units of s−1s−1.Part (b) Determine the initial number of nuclei strontium-91 nuclei initially in the sample.Part (c) Determine the activity in units of becquerel after 18 hours.