A thin, nonconducting rod of length \(L\) lies along the positive \(x\)-axis with its left end at the origin \(x = 0\). The rod has a non-uniform linear charge density given by \(\lambda(x) = \beta x\), where \(\beta\) is a positive constant and \(0 \le x \le L\). Point \(P\) is located on the \(x\)-axis at \(x = D\), where \(D > L\). Assuming the electric potential is zero at infinity, which of the following expressions represents the electric potential \(V\) at point \(P\)?