CONCEPT: Area of a triangle = (1/2)* a* b* sin (angle included between a and b) where
a and b are two sides of the triangle.
The sine formula for area can also be used here to find the area.
Sine formula for area = (1/2)*a*b*sin(included angle)
= (1/2)*5*12*sin 90
=30 sq units (OPTION D)