A gas is allowed to expand in a well insulated container against a constant external pressure of 2.5 atm from an initial volume of 2.50 L to a final volume of 4.50 L. The change in internal energy $\Delta U$ of the gas in joules will be -

Question

( A ) $+505 \; J$
( B ) $-500 \; J$
( C ) $1136.25 \; J$
( D ) $-505 \; J$