zssp, Sean,
If indeed you did fail instruments because of this question, then you have a good case to protest - none of the answers are correct.
Please forgive the degree of decimal places, included so that this can be proven conclusively.
The basic mathematics indicate that the said time intervals may only be achieved at a TAS of 119.293656 Kt, and a Wind Component of -10.20274691 Kt on the first leg, and conversly +10.20274691 Kt on the second, i.e. a Groundspeed outbound of 109.0909091 Kt, and 129.4964029 on return. Apply these Ground Speeds to the 5 nm between pylons without ANY rounding off of the results -
5 nm at G/S 109.0909091 = 2:45 EXACTLY
5 nm at G/S 129.4964029 = 2:19 EXACTLY
OK, a TAS of 119.293656 Kt is proven. At 7000 feet Pressure Height and a Static Air Temperature of +15°C. To achieve the quoted TAS in these conditions requires EAS 104.79, Mach No. 0.1803, or, importantly for you, a CAS of 104.8868949.
Thus, if the flight is conducted at 100 KIAS, the ASI is UNDER-READING by 4.8868949 Kt, 5 Kt between friends.
NONE of the answers are correct. Protest the result Sean, protest!
Regards,
Old Smokey