In the isothermal expansion of 10 g of gas from volume V to 2V the work done by the gas is 575 J. What is the root mean square speed of the molecules of the gas at that temperature?\\
(1) $398 \mathrm {~m} / \mathrm { s }$\\
(2) $520 \mathrm {~m} / \mathrm { s }$\\
(3) $499 \mathrm {~m} / \mathrm { s }$\\
(4) $532 \mathrm {~m} / \mathrm { s }$