If X, the Time (In Minutes)to Complete an Oil Change $\le$

Multiple Choice

If x, the time (in minutes) to complete an oil change job at certain auto service station, is uniformly distributed over the interval 20 to 30, inclusively (20 $\le$ x $\le$ 30) , then the height of this distribution, f(x) , is __________________.

A) 1/10
B) 1/20
C) 1/30
D) 12/50
E) 1/60