At exactly what time past 5:00 will the minute and hour hands of an accurate working clock be precisely perpendicular to each other for the first time?  Choose the correct choice.
A) 20 13/21 minutes past 7:00  B) 20 13/17 minutes past 7:00  C) 21 3/23 minutes past 7:00  D) 21 9/11 minutes past 7:00  E) 22 4/9 minutes past 5:00
A1 = hour angle   A2 = minute angle   A1-A2 = 90   Assume the minutes = M   A1 = (5*60+M)/12*60 )*360   A2 = M*360/60   Solving all three equation , results in the answer 22 4/9 minutes past 5:00
<result>E</result>
At exactly what time past 5:00 will the minute and hour hands of an accurate working clock be precisely perpendicular to each other for the first time?