the complete question in the attached figure
we know that
[volume of a prism]=L*W*H
first type of prism measures 3 inches by 6 inches by 14 inches
then
[volume first type of a prism ]=3*6*14----------> 252 in³
second type of prism measures 15 inches by 5 inches by 10 inches
then
[volume second type of a prism ]=15*5*10----------> 750 in³
[volume of the figure]=2*[volume first type of a prism ]+[volume second type of a prism ]
[volume of the figure]=2*252+750---------> 1254 in³
the answer is 1254 in³