[问答题]
$\text { A right cylinder has height } h \mathrm{~mm} \text { and diameter } x \mathrm{~mm} \text {. The volume of this cylinder is equal to } 45 \mathrm{~mm}^{3} \text {. }$
The total surface area, A , of the cylinder can be expressed as $A=\frac{\pi}{2} x^{2}+\frac{k}{x} $.
1. Find the value of k .
2. Find the value of x that makes the total surface area a minimum.
