A battery of silicon photocells mounted on a plane surface operates with an efficiency of 16.7% under all conditions encountered in this problem. it is installed at a location 45 degrees north. the time is 10:00 on April 1, 1995. When the battery faces the sun directly it delivers 870 W to a resistive load. How much power does it deliver if the surface is setset at an elevation of 25 degrees and faces true east?