A soap bubble of surface tension 0.04 N / m is blown to a diameter of 7 cm. If (15000-x) μ J of work is done in blowing it further to make its…

A soap bubble of surface tension $\displaystyle 0.04 \mathrm{~N} / \mathrm{m}$ is blown to a diameter of $\displaystyle 7$ cm . If $\displaystyle (15000-x) \mu \mathrm{J}$ of work is done in blowing it further to make its diameter $\displaystyle 14$ cm , then the value of $\displaystyle x$ is $\displaystyle \_\_\_\_$. ( $\displaystyle \pi=22 / 7$ )