As the two solids are congruent it can be said that they have the same angles and the same lengths then their volume is equal and therefore S1= S2 then S1∪S2= S1+S2- S1∩S2 = S1+S1- S1∩S2 =2S1- S1∩S2 =25.
Now, S1∩ S2= Prism volume= (Area of triangle (A)*Height(h)), the area of the equilateral triangle that is the base of the prism is given by A=√3/4*(length Lateral) ^2= A=√3/4*(2^2 )=√3 square units .
