A patient presents with a refraction of -2.50 +0.75 x 90. He wants to be fit into a hard contact lens. His K readings are vertical 7.65 mm of radius (44.12 D @ 90) and 7.8 mm of radius (43.25 D @180). You chose to put a 7.65 mm radius of curvature contact lens on him. What should be the final spherical power of the hard contact lens?