46. During the first shift of a 24-hour operation with a 2-shifting schedule, a drill machine was in operation for 10.5 hours and underwent repairs for 0.5 hours, within this time frame, the drill machine achieved a production of 251 meters. Calculate the percentage utilization of the drill machine during the first shift
a. 86%
b. 87%
c. 88%
d. 89%
e. None of these