By how many folds the temperature of a gas would increase when the root mean square velocity of the gas molecules in a container of fixed volume is increased from $5 \times 10 ^ { 4 } \mathrm {~cm} / \mathrm { s }$ to $10 \times 10 ^ { 4 } \mathrm {~cm} / \mathrm { s }$ ?\\
(1) Two\\
(2) Three\\
(3) Six\\
(4) Four