Smith has to cover a distance of 84 km in 40 minutes. If he covers one-half of the distance in one-fourth of the total time, to cover the remaining distance in the remaining time, what should be his speed in km/hr?

(A) 42 Km/hr
(B) 84 Km/hr
(C) 90 Km/hr
(D) 100 Km/hr