Need help with this total surface area and stationary point question (image attached)

a.

b. 288 sq units

Step-by-step explanation:

Given the dimensions of the base sides and the cuboids volume, we can calculate its height:

Having determined h=.

The surface area of the cuboid is the sum of all its faces area;

=A, hence, proved!

b. Find stationary value of A

We find the critical point  of the function:

Hence, x is undefined. The stationary area is therefore calculated as:

The area is 288 sq units

in geometry, parallel lines are lines in a plane which do not meet; that is, two lines in a plane that do not intersect or touch each other at any point are said to be parallel. by extension, a line and a plane, or two planes, in three-dimensional euclidean space that do not share a point are said to be parallel.