Answer:

Explanation:
Given:
Initial mass of isotope (m₀) = 20 g
Half life of the isotope
= (ln 4) years
The general form for the radioactive decay of a radioactive isotope is given as:

Where,

So, the equation is: 
At half-life, the mass is reduced to half of the initial value.
So, at
. Plug in these values and solve for 'k'. This gives,

Hence, the equation for the mass remaining is given as:

<span>Without convection, the equator would stay smoldering hot, the poles would stay well in the deep freeze, and places in between would be in between. The currents move the warm air and warm water from the tropics up to the poles and move cold air and water from the poles down to the tropics. Until now, the coasts have enjoyed milder weather because of the convection currents. -Hope this helps!</span>