Low degree rational curves on quasi-polarized K3 surfaces

We prove that there are at most (24-r_0) low-degree rational curves on high-degree models of K3 surfaces with at most Du Val singularities, where r_0 is the number of exceptional divisors on the minimal resolution. We also provide several existence results in the above setting (i.e. for rational curves on quasi-polarized K3 surfaces), which imply that for various values of r_0 our bound cannot be improved.