try this
Dear Sirs
I refer you to the recent exam paper in which students are expected to deduce an IAS error. From the data given that an aircraft is at 7000ft pressure altitude, an air temperature of 15 deg C and accomplishes 5 nautical mile outbound and inbound legs in 2min 45secs and 2min 19secs respectively it can be deduced that true airspeed is 119 knots. If the IAS calibration is correct it should therefore read 105knots but it reads 100kts instead. This is under-reading by 5 knots but no such option is given in the multiple-choice selection. Even if the erroneous assumption is made that true airspeed is total distance divided by total time (it is of course deduced from outbound and inbound speeds calculated separately) it is not possible to mistakenly select a value from the range offered. As the aircraft is supposed to reverse its route and not fly a reciprocal bearing (which in wind would not take it back to its starting point) drift is not an issue. I am therefore at a loss as to how the examiner who drafted the question expects it to be answered. I await your reply with interest.