Answer and Explanation:
Exposure time in an X-ray can be Calculated as the difference of the two set levels.
Therefore to calculate the exposure time:
The difference of the two current levels is equal to exposure time
(200mA - 15mA) = 185 mA
Exposure time = 185 mA
(There is a direct relationship between mA and time. Thus, a higher mA setting corresponds to a reduction in required exposure time).