An element has two naturally occurring Isotopes. The mass numbers of these isotopes are 109.00 u and 111.00 u, with natural
abundances of 20% and 80%, respectively. Calculate its average atomic mass, Report your answer to 2 decimal places.

Ok where is the image ?

The answer you are looking for is option d

The internal energy of the system we can term it as total potential energy and kinetic energy. energy flows out of the surrounding from the system then we can say that the internal energy of the final state is lower than its initials. the sign of  δesystem is negative.δesystem = efinal - einitial=-ve  efinal  ∠einitial.