Estimate the theoretical fracture strength of a brittle material if it is known that fracture occurs by the propagation of an elliptically shaped surface crack of length $0.5 \mathrm{mm}(0.02 \mathrm{in.})$ and having a tip radius of curvature of $5 \times$ $10^{-3} \mathrm{mm}\left(2 \times 10^{-4} \mathrm{in.}\right),$ when a stress of $1035 \mathrm{MPa}(150,000 \mathrm{psi})$ is applied.