4. The first three terms in the expansion in descending powers of \(x\) of
$$\left( x + \frac { k } { x ^ { 2 } } \right) ^ { 15 } ,$$
where \(k\) is a constant, are
$$x ^ { 15 } + 30 x ^ { 12 } + A x ^ { 9 } .$$
- Find the values of \(k\) and \(A\).
- Find the value of the term independent of \(x\) in the expansion.