1 mole of ideal gas is allowed to expand isothermally from the initial volume of 1L to 10L, the value of $\Delta U$ for the process is $(R = 2\: cal/Kmol)$

Question

$\begin {array} {1 1} (A)\;163.7\: cal & \quad (B)\;1382.1\: cal \\ (C)\;9\: L-atm & \quad (D)\;Zero \end {array}$