public static void main ( String [ ] args ) {
  int cases = sc . nextInt ( ) ;
  for ( int i = cases ;
  i != 0 ;
  i -- ) {
    long n = 0 , res = 0 ;
    long a = sc . nextLong ( ) , b = sc . nextLong ( ) , k = sc . nextLong ( ) ;
    if ( k % 2 == 1 ) {
      n = k / 2 + 1 ;
      res += n * a - ( n - 1 ) * b ;
    }
    else {
      n = k / 2 ;
      res += n * a - n * b ;
    }
    System . out . println ( res ) ;
  }
}

public static void main ( String [ ] args ) { int cases = sc . nextInt ( ) ; for ( int i = cases ; i != 0 ; i -- ) { long n = 0 , res = 0 ; long a = sc . nextLong ( ) , b = sc . nextLong ( ) , k = sc . nextLong ( ) ; if ( k % 2 == 1 ) { n = k / 2 + 1 ; res += n * a - ( n - 1 ) * b ; } else { n = k / 2 ; res += n * a - n * b ; } System . out . println ( res ) ; } }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (identifier))) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (identifier))) condition: (binary_expression left: (identifier) right: (decimal_integer_literal)) update: (update_expression (identifier)) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal)) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (decimal_integer_literal))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (decimal_integer_literal)))) (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (binary_expression left: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (identifier)))))) alternative: (block (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (decimal_integer_literal)))) (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (binary_expression left: (identifier) right: (identifier))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))))