Problem: what is the unit digit in 7105 ?
Rationale: "unit digit in 7105 = unit digit in [ ( 74 ) 26 * 7 ] but , unit digit in ( 74 ) 26 = 1 unit digit in 7105 = ( 1 * 7 ) = 7 answer : c"
annotated_formula: circle_area(divide(7105, multiply(const_2, const_pi)))