Correct option is (A) 59
Given, total number of rows is 214 and time taken to perform one refresh operation is 50 nanoseconds.
So, total time taken to perform refresh operation = 214*50 nanoseconds = 819200 nanoseconds = 0.819200 milliseconds.
But refresh period is 2 milliseconds.
So, time spent in refresh period in percentage
= (0.819200 milliseconds) / (2 milliseconds) = 0.4096 = 40.96%
Hence, time spent in read/write operation = 100% – 40.96% = 59.04% = 59 (in percentage and rounded to the closet integer).