given this function: int sum nums(int total, pair p) { return total (p.first * p.second); } what is the value of the variable named sum after the following code is executed? multimap nums{ {2, 10}, {3, 20}, {3, 30}, {4, 40} }; int sum = accumulate (nums. begin(), nums.end(), 0, sum_nums); a. 100; b. 200; c. 330; d. 1200