Msq. a radioactive sample emits n b-particles in 2 sec. in next 2 sec it emits 0.75n b- particles, then which of the following statements are true (in2 -0.693

A radioactive sample emits n B-particles in 2 sec. In next 2 sec it emits 0.75n B- particles, then which of the following statements are true (In2 -0.693, In3 =1.0986) (a) Decay constant of the sample is 0.14sec (b) Decay constant of the sample is 0.28 sec (c) Mean life of the sample is 3.5 sec (d) Mean life of the sample is 7.0 sec