| using namespace std; | |
| int tc, n; | |
| double a[3010], c[3010]; | |
| int main(){ | |
| scanf("%d", &tc); | |
| while(tc--){ | |
| scanf("%d", &n); | |
| scanf("%lf %lf", &a[0], &a[n+1]); | |
| for(int i = 1; i <= n; i++) scanf("%lf", &c[i]); | |
| double sum = 0; | |
| for(int i = 1; i <= n; i++) sum += 2 * i * c[n + 1 - i]; | |
| double ans = n * a[0] + a[n + 1] - sum; | |
| ans /= n + 1; | |
| printf("%.2lf\n", ans); | |
| if(tc) putchar('\n'); | |
| } | |
| return(0); | |
| } | |