Units of rate constant of first and zero order reactions in terms of molarity M unit are respectively

$$\beta$$ - particle is emitted in radioactivity by

If half-life of a substance is 5 yrs, then the total amount of substance left after 15 years, when initial amount is 64 grams is

For the reaction A + 2B $$\to$$ C, rate is given by R = [A] [B]² then the order of the reaction is