For 30 consecutive days, the daily high temperature was recorded. On each of the first 25 days, the temperature recorded was 21^{\circ} \mathrm{C}. On each of the remaining 5 days, the temperature recorded was 15^{\circ} \mathrm{C}. For the 30 days, the mean (average) of the temperatures recorded was
Answer Choices
A. 17^{\circ} \mathrm{C}
B. 19^{\circ} \mathrm{C}
C. 20^{\circ} \mathrm{C}
D. 16^{\circ} \mathrm{C}
E. 18^{\circ} \mathrm{C}