The unit rate is 140 kilobytes/sec, is the answer.
Detailed explanation:
The unit of measurement used in computing to assess the rate at which data is transferred across a network is kilobytes per second. All that is needed to compute the rate is to divide the kilobytes by the time. Broadly speaking, it may be stated that higher network bandwidth corresponds to faster data transmission. The following method of calculation can be used:
140 kilobytes/second = 2520 kilobytes/18 seconds