The first three terms, in descending powers of \(x\), of the expansion of

\(\left(ax+\frac25\right)^5\left(1-\frac{b}{x}\right)^2\)

can be written as

\(32x^5-160x^4+cx^3,\)

where \(a\), \(b\) and \(c\) are constants. Find the exact values of \(a\), \(b\) and \(c\).