Which of the given set of planes are perpendicular to each other?

• A. ( vec{r}.(2 hat{i}+2 hat{j}+ hat{k}) )=5 and ( vec{r}.( hat{i}+2 hat{j}+2 hat{k}) )=5
• B. ( vec{r}.( hat{i}-2 hat{j}+ hat{k}) )=7 and ( vec{r}.( hat{i}+ hat{j}+2 hat{k}) )=2
• C. ( vec{r}.(2 hat{i}-2 hat{j}+ hat{k}) )=4 and ( vec{r}.( hat{i}+2 hat{j}+2 hat{k}) )=5
• D. ( vec{r}.(3 hat{i}-2 hat{j}+ hat{k}) )=2 and ( vec{r}.( hat{i}+2 hat{j}+8 hat{k}) )=8