It is known that the presence of interstitials can cause significant strengthening in some body-centered-cubic metals, for example, carbon in iron and nitrogen in niobium. Yield strengths of high-purity niobium and a niobium containing 0.01 atomic % of nitrogen are 200 and 260 MPa, respectively. If you have a piece of niobium from a supplier, which contains 0.5 atomic % of nitrogen, what is its estimated yield strength?