• A weather balloon contains $5600$m$3$ of helium $($He$)$ at a pressure of $1\mathrm{.}25$times $10\mathrm{⁵}$ Pa$.$ The temperature of the helium is $7.$ Data regarding helium can be found in the periodic table of elements.

  a$)$ What is the mass $($in kg$)$ of the helium in the balloon $?$

  b$)$ The balloon rises and expands to a new volume of $7200$m$\mathrm{³}$ At the same time ,the temperature drops to $5.$ Calculate the new pressure of the gas.