This Go code processes orders concurrently but occasionally produces incorrect totals. Find and fix all concurrency issues. ```go package main import ( "fmt" "sync" ) type OrderProcessor struct { totalRevenue float64 orderCount int errors []string } func (op *OrderProcessor) ProcessOrder(amount float64, wg *sync.WaitGroup) { defer wg.Done() if amount <= 0 { op.errors = append(op.errors, fmt.Sprintf("invalid amount: %.2f", amount)) return } op.totalRevenue += amount op.orderCount++ } func main() { op := &OrderProcessor{} var wg sync.WaitGroup orders := []float64{99.99, 149.50, -10.00, 299.99, 49.99, 0, 199.99} for _, amount := range orders { wg.Add(1) go op.ProcessOrder(amount, &wg) } wg.Wait() fmt.Printf("Total: $%.2f from %d orders\n", op.totalRevenue, op.orderCount) } ```