In the nuclear reaction $_{92}U^{238} \to _{Z}Th^{A} + _{2}He^{4}$,the values of $A$ and $Z$ are:

$A$ free neutron decays spontaneously into :

When a radioactive isotope ${}_{88}^{228}Ra$ decays in series by the emission of $3$ alpha particles and $1$ beta particle,the isotope finally formed is

In the given reaction $_Z{X^A} \to _{Z+1}{Y^A} \to _{Z-1}{K^{A-4}} \to _{Z-1}{K^{A-4}}$,radioactive radiations are emitted in the sequence:

The radionuclide $^{11} C$ decays according to
$_{6}^{11} C \rightarrow_{5}^{11} B + e^{+} + \nu: \quad T_{1/2} = 20.3 \; min$
The maximum energy of the emitted positron is $0.960 \; MeV$. Given the mass values:
$m(_{6}^{11} C) = 11.011434 \; u$ and $m(_{5}^{11} B) = 11.009305 \; u$
Calculate $Q$ and compare it with the maximum energy of the positron emitted.

$A$ certain radioactive material can undergo three different types of decay,each with a different decay constant $\lambda_1$,$\lambda_2$,and $\lambda_3$. Then the effective decay constant is: